Pascal pointed me to this unique item - the PCE Pro, a flash multi-cart for the PC Engine/Turbo Grafx across all territories (with NTSC and PAL support too!). It has a rudimentary OS which allows multiple games to live on the 32 meg flash cart simultaneously (up to 31), and supports cheat codes, some of which Tototek supplies here. The cart also supports the 20 meg games (Street Fighter II'). The site has pictures of the cart inserted in all sorts of PCE devices, but as far as I know, Supergrafx games are still not supported.

The creator of the PCE Pro is Biu, an ex Lik-Sang fellow, and was the originator of some of the later grey market products they manufactured. Biu is now only working with the classics, though. None of his many products have cases, so he uses scotch tape to protect his PCE Pro. Good stuff. There's lots of other interesting tech to look at on the site, such as the game gear flash cart (good for playing Sylvan Tale with the english hack. Hey, you could do that anyway!), complete with instructions for how to make your own rudimentary case from a spare GG cart.

Update! Thanks to Tobias and Lawrence for pointing out this PCE flash cart. It's a bit more elegant, has 64 megs of space, comes with a docking station, and also supports Supergrafx games. Unfortunately it's only available in Japan, so finding one would be tough, unless someone picks it up for larger sale.