Hello! Welcome to the Forums!
Well, to answer your question, yes there are some stores that sell Giantmicrobes, but very few. Your best bet is to go find some science museums, and look in their gift shops, but other than that, you'll have to search in toy stores or malls... hmm... you know, sometimes airports have them...
Anyway, if you live near the Great Lakes, you might find some luck, otherwise, you'll have to rely on the internet... Sorry, this is all the info I can give you
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