CapnJim really does have the best idea so far - 15mm was always a more popular ww2 scale in the US, 20mm more a UK/European scale. The Zvezda gun and infantry packs for their ww2 series of games are 20mm (whilst the vehicles are 15mm - no I don't understand either) and are in a slightly firmer plastic than the usual soft plastic sets - well worth a look if you can find them, although the emphasis is mostly Soviet/German forces.
Failing that, all I can suggest is that you email US distributors of, say, Wargames Foundry and see if they'd include ww2 figures in their next order - I know there are a few US retailers that occasionally stock Foundry (I don't know of any others). Force 20 figures are available in the US but I don't know what figures they do in their ww2 range. Not a lot of help, I know, but good luck.