does anyone know where I can get a pembom, pengebom jaket like Americas?????

Hmm lets see... Expensive way:Ebay atau something like that. Hard way: Attempt to make it atau find someone to make it for you.. atau the Easy way! lol Find a cheap jacked that looks close to it and duct tape the 50 to the back of it! I was close to doing that myself XD Its cool that anda have the rest of the outfit :P (not the best answer but its some choices)

If your actually buying the cosplay outfit itself, try ebay, atau amazon (I haven't check amazon, but i'm obsessed with amazon. it has almost everything...)
But anda may find this shocking, but anda can actually find a bombers jaket like Alfred's at the mall. try checking the stores. But really, my friend dressed up as Alfred with searching handpicked items, she got a bomberjacket at the mall, went to a fabric store, got the number 50, got a star, and a airplane, amde out of patches, put them on. And it came below 25 dollars.

I saw some on Ebay.

cosplays aren't always that comfortable though online...I'd say it's better to find a pembom, pengebom jaket style jaket at clothes stores and add the 50 on the back, the bintang on the left front side and the airplane on the left shoulder/sleeve... I helped my friend with her America jaket (her sister helped as well). it looks quite amazing!