Use scrapy to get list of urls, and then scrape content inside those urls

I need a Scrapy spider to scrape the following page (https://www.phidgets.com/?tier=1&catid=64&pcid=57) for each URL (30 products, so 30 urls) and then go into each product via that url and scrape the data inside.

I have the second part working exactly as I want:

import scrapy

class ProductsSpider(scrapy.Spider):
    name = "products"
    start_urls = [
        'https://www.phidgets.com/?tier=1&catid=64&pcid=57',
    ]

    def parse(self, response):
        for info in response.css('div.ph-product-container'):
            yield {
                'product_name': info.css('h2.ph-product-name::text').extract_first(),
                'product_image': info.css('div.ph-product-img-ctn a').xpath('@href').extract(),
                'sku': info.css('span.ph-pid').xpath('@prod-sku').extract_first(),
                'short_description': info.css('div.ph-product-summary::text').extract_first(),
                'price': info.css('h2.ph-product-price > span.price::text').extract_first(),
                'long_description': info.css('div#product_tab_1').extract_first(),
                'specs': info.css('div#product_tab_2').extract_first(),
            }

        # next_page = response.css('div.ph-summary-entry-ctn a::attr("href")').extract_first()
        # if next_page is not None:
        #     yield response.follow(next_page, self.parse)

But I don't know how to do the first part. As you will see I have the main page (https://www.phidgets.com/?tier=1&catid=64&pcid=57) set as the start_url. But how do I get it to populate the start_urls list with all 30 urls I need crawled?