Hi! When we bought Mattias wig for his America cosplay, we simply searched ebay for "america cosplay wig hetalia" or something similar. We got a pre-styled wig (with the "curl" especially sown in) which we then cut and restyled so the length and shape fit Mattias face. I am sad to note that the seller we bought from is no longer active, but there should be other wigs which could fit your needs. If you only find the right colour and not the right cut and styling, you can always have a look at Mattias
wig cutting tutorial for some guidelines for how to cut it ^^
Good luck, and we hope you have fun cosplaying!