Looking to gauge interest on this, I’ve got a spare Wonderswan Flash Masta. Early model, not the newer one with the 3D printed shell. Just a bare PCB, but feature-identical otherwise. Ideal for playing those ultra-expensive games like Judgement Silversword and Dicing Knight. Bear in mind that this is not quite an everdrive-tier flashcart, there are several slots for games but only one slot for saves. This is still true of the revisions they’re selling afaik.
It’s not a perfect solution by any means, but it’s good for the expensive stuff, tetris, gunpey, and so on where saves aren’t so important. As far as I know there isn’t a better alternative out as far as flash carts for the wonderswan go. Wanted to do an interest check here instead of immediately throwing it up on ebay.