NWN make good quality ones, for sure. I only own one from them, but it's made with a nice, fine polyester weave and crisp printing:
I've ordered a bunch of music and merch direct from Yasuyuki of Abigail/Barbatos/12 other bands too, and if you like his music, he also offers really nice quality merch on his official site. I have an
Intercourse and Lust banner with the "The Dream of the Fisherman's Wife" painting on it and it looks great. Same quality/likely the same manufacturer. It might even be distributed by NWN directly for all I know, not that I'm encouraging anyone to give Yosuke more money... The Japanese yen is at an all-time low, so Yasuyuki's prices are not bad, even with international shipping.
Conversely, I hate to say it, but I ordered some from Necroharmonic during a couple of sales, and they're really bad quality... Blurry, low-dpi JPEG images with horrible artifacting. Coarsely woven polyester. They're affordable for a reason... it's not music-related, but I have a really blurry Faces of Death Pt. II one from him that I'm never going to hang up anywhere if you want it
Also, I haven't forgotten drunkenly asking you to send me collab source material probably over a year ago, I just work very slowly in between binges and blackout periods. One of these days!
PS: Maybe you can email NWN to ask where they get theirs done.
