How to implement different volumes for 1 product?

Question

Django

Good day.
I am making a store and I need to implement different volumes for one product. Eg. 100 ml, 500 ml, 1 liter, etc. The product page should have a drop-down menu to select the desired option.
There is an idea to make a separate product for each size. But how then on the product page, in this selection menu, to show the rest of the variations of this product?
========UPD========
All product information is stored in the Product model. And all prices are in the StockRecord model. One product can have several StockRecords. This is due to the fact that there are 5 sites that are on the same database. And on different sites there may be different prices (StockRecords)
Thank you in advance for your help.

Answer 1

Related packaging table

Answer 2

Something like this:

products
id, name, description, ...

product_types
id, product_id, name, price, ...

Answer 3

Here it is better to agree with the customer, as he may have his own experience and thoughts about keeping sales statistics and other things that you did not immediately ask or did not specify

Shop
  name

Product:
  name

StockUnit
  name
  size

StockUnitInShop
  sku
  count_in_shop
  product = FK(Product)
  shop = FK(Shop)

Answer 4

You already have it implemented in Oscar.