Django: need to render form options manually

I need to replicate this form:

Live web page URL:

https://www.stickermule.com/products/die-cut-stickers

I've been reading the docs on how to render fields manually, but cannot render the radio inputs and their values manually.

https://docs.djangoproject.com/en/2.1/topics/forms/#rendering-fields-manually

My problem specifically is with the "Select a quantity part".

1) My form inherits from forms.ModelForm and only contains the quantity, not the cost (in $) neither the savings part.

That's why I need to put the quantity in a tag, pulling it from the form, and use other 2 tags in pure html to manually put the cost and the savings.

Unless there is a way to put these values in the model as others fields, but related to the field quantity (cantidad, in Spanish).

Desired HTML:

Copied from this page I need to replicate:

https://www.stickermule.com/products/die-cut-stickers

<form>
<div id="variants" class="product-option-group">      
 <legend>Select a size</legend>
 <ul id="variant-options" class="options">
   <li>
      <input id="variant_79" name="variant_id" readonly="" type="radio" value="79">
      <label for="variant_79"> 2" x 2"</label>
   </li>
   <li>
      <input id="variant_78" name="variant_id" type="radio" value="78">
      <label for="variant_78"> 3" x 3"</label>
   </li>
   <li>
      <input id="variant_80" name="variant_id" type="radio" value="80">
      <label for="variant_80"> 4" x 4"</label>
   </li>
   <li>
      <input id="variant_81" name="variant_id" type="radio" value="81">
      <label for="variant_81"> 5" x 5"</label>
   </li>
   <li>
      <input id="variant_77" name="variant_id" type="radio" value="77">
      <label for="variant_77"> Custom size</label>
   </li>
 </ul>
</div>
<div id="quantities">
   <legend>"Select a quantity"</legend>
   <ul>
      <li>
          <span class="table-cell">
            <input type="radio">
            <label>50</label>
          </span>
          <span id="price_50_id" class="table-cell  price">$57</span>
          <span class="table-cell savings"></span>
      </li>
      <li class=" quantity-item">
          <span class="table-cell">
              <input id="quantity_100" readonly="" name="quantity" type="radio" value="100">
              <label for="quantity_100" class=" quantity"> 100</label>
          </span>
          <span id="price_100_id" class="table-cell   price">$69</span>
          <span class="table-cell savings">Save 39%</span>
       </li>
  </ul>
</div>

models.py:

class TamaniosCantidades(models.Model):
    TAMANIOS = (('2x2', '2" x 2"',), ('3x3', '3" x 3"',),
               ('4x4', '4" x 4"',), ('5x5', '5" x 5"',))

    CANTIDADES = (('50', '50',), ('100', '100',),
                ('150', '150',))

    tamanios = models.CharField(max_length=10, choices=TAMANIOS)
    cantidades = models.CharField(max_length=10, choices=CANTIDADES)

forms.py:

class TamaniosCantidadesForm(forms.ModelForm):
    tamanios = forms.ChoiceField(choices=TAMANIOS, widget=forms.RadioSelect(), label='Selecciona un tamaño')
    cantidades = forms.ChoiceField(choices=CANTIDADES, widget=forms.RadioSelect(), label='Selecciona la cantidad')
    class Meta:
        model = TamaniosCantidades
        fields = ['tamanios', 'cantidades']

    def __str__(self):
        return self.tamanios

My HTML:

<form action="/post_url_tamanioscantidades/" method="post">
    {% csrf_token %}
    {{ tamanioscantidades_form.as_p }}
    <input type="submit" value="Submit"/>
</form>

In Summary:

I would like to call the fields like:

<form>
   <div id="quantities">
     <legend> {{ tamanioscantidades_form.label }} </legend>

     <ul>
        <li>
        <span>
             <input type="radio" id="{{ tamanioscantidades_form.input1_id }}>
             <label> {{ tamanioscantidades_form.label }} </label>
        </span>
        <span>
             <label>$57</label>
        </span>
        <span>
             <label>""</label>
        </span>
       </li>
     </ul>
    </div>
</form>

UPDATE 1:

With the answer from I can now render the radio button, but not the label.

class TamaniosCantidadesForm(forms.ModelForm):
    tamanios = forms.ChoiceField(choices=TAMANIOS, widget=forms.RadioSelect(), label='Selecciona un tamaño')
    cantidades = forms.ChoiceField(choices=CANTIDADES, widget=forms.RadioSelect(), label='Selecciona la cantidad')
    class Meta:
        model = TamaniosCantidades
        fields = ['tamanios', 'cantidades']

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.cantidades_options = [option for option in self['cantidades']]

    def __str__(self):
        return self.tamanios

HTML:

The label from the first option {{ tamanioscantidades_form.cantidades_options.0.label }} won't render

<ul>
  <h1>{{ tamanioscantidades_form.cantidades.label }}</h1> #This renders
  <li>
     <span> {{ tamanioscantidades_form.cantidades_options.0.tag }}
     <label> {{ tamanioscantidades_form.cantidades_options.0.label }} </label> #This does not render
   </span>
 </li>