I've used and can recommend the following, in no particular order.
Arcade Art Repro - https://arcadeartrepro.com
High quality reproductions of artwork, plexiglass, control panels etc. I've used Barry's stuff for both my Astro City and SNK U4 refurbs. Based in the Netherlands so shipping can be expensive.
Mikonos11 (Zona Arcade)
Very good at custom requests, repro artwork and stickers. Probably the closest to 'original' when it comes to Japanese stuff (in my experience)
Arcade Art Shop - https://www.arcadeartshop.com
Another very good shop, useful mix of NOS art, reproductions (include NNC side arts), case labels, screws etc.