Google Sheets - Combine VLOOKUP with Named Ranges to create Drop Down

I have 3 worksheets - Stock, Products and Sizes.

I have created 3 named ranges:
Adults
Kids
Shoes

On the 'Stock' worksheet, once a product has been added - I'd like the size column to become a drop down containing the correct sizes for that product - based on the named range set in 'Products'.

EXAMPLE
Product redshirt1 in Products has been assigned a range of Adults.
Therefore, the following cell should contain a drop down with the following sizes: L, XL, XXL

Screenshot 2022-01-16 134847.png

I hope that's clear enough, thanks in advance for any help.

Here is my Google Sheet:
https://docs.google.com/spreadsheets...it?usp=sharing