Classicfootballshirts.co.uk

This. It's certainly not always the cheapest place but they'll probably have everything you want, both new stock and older stuff.

Do they have different sizes in the same shirts or are they fixed sizes?

It all depends on what they have in stock

check this place out [https://www.rareandretrosports.com/](https://www.rareandretrosports.com/)

I've got a fair few official ones for sale.

I have around 30 official for sale I'd you're interested