Non linear fixed quantity

I can see others are asking this but I havent seen anyone answer it clearly, if at all. ( sorry if I have missed it).

I want customers to only choose a combination of 2, 4, 8, or 10 and products of that above 10. But I cant see how to do that with woocommerce. I can fix the minimum, I can set a step (but I dont want a fixed step).

any ideas on how to do this? Happy to use a plugin.