I bought my last short valve Schrader tubes from Decathlon, and I was quite pleased to find them because most of my bikes have shallow rims, and with a 20" wheel a long valve looks clunky.

Of course, Schrader and Presta are not the only choices, I was in my local DIY store here in Poland the other day and they still offer tubes with Dunlop/Woods valves, which is handy as I cannot for the life of me find a Schrader-sized pump-to-valve connector tube and it is so easy to misplace all your convertors when you need one.