There’s now an eBay seller listing a sub-$40 do-it-yourself MVS “supergun” kits for any Neo Geo MVS board that uses the JAMMA standard (I believe mostly MV1B & MV1C). The creator previously sold some high quality MiSTer boards and has recently moved on to other projects, including this one.
While I haven’t had a chance to personally test one, it looks like a very basic (mean that in a good way) board that attenuates the high-voltage arcade RGBs signal down to console-level and outputs via a Neo Geo DIN-C port. There’s also POT’s to adjust each color and an On/Off switch…which is surprisingly missing from many supergun solutions. The device can power your board with a standard PSU molex connector, or if you perform a mod, you can use a 5v barrel PSU.
As with almost every supergun sold, I STRONGLY recommend testing the video and audio output on an oscilloscope before plugging it into any equipment!!! This will guarantee that your monitors, scalers and switches will be safe to use, with the added bonus of calibrated video output and audio that won’t clip! More info can be found in the oscilloscope section of the site: https://www.retrorgb.com/oscilloscope.html
There are no pre-assembled superguns in the store, but there are three versions of the kit available: