Heyooo,
I’m currently getting my metal/battle vest ready for W:O:A this year and I would love to get my hands on more patches of japanese bands to represent j-rock & metal a bit more. 
Do you know any online shops who sell patches of japanese bands? I only got X Japan and MUCC (fanmade by my mother haha <3) so far… I guess they aren’t really common in japan? Already checked some official merch shops but no luck so far. 
Had the same struggle for my vest.
There are really just a few Japanese bands which produce patches. I also did them for myself. My backpatch is made from a DEG shirt. I also just ordered a Lunacy patch as they sold some on the last Lunacy event - but that’s it.
I will keep an eye on a VK vest this WOA then. 
If you want metal and punk patches Etsy is your best choice IMO. Got loads of Japanese stuff for a pretty price there.
When it comes to unofficial patches, let me only mention that vk.gy has quite a few high quality logos added to band profiles so you can source these for your patches ^^