Lynx
http://atariage.com/forums/topic/250637-lynx-multi-card-preorders/
NeoGeo Pocket
http://www.retrohq.co.uk/neogeo-pocket-pre-order
Wonderswan
http://www.flashmasta.com/product/ws-flash-masta-usb-cartridge-for-wonderswan/
Nomad
Just use a Mega Everdrive.
Problem with this is the Lynx and Neo Geo Pocket cart producer has a huge waiting list. Krikzz seems to have a much better grasp on how to mass produce these things in high quallity. The wonderswan cart appears to be more readily available, but its extremely barebones. I would like to see everdrives for these systems with a nicer menu system, cheats, save states, on the fly IPS patching, etc and of course the high quallity and availability we have come to expect from krikzz. In addition, if possible, it would be great if an everdrive neo geo pocket color could be made without the extreme delay (wayyyyyyyy longer than any everdrive) required to move roms from sd to flash so they can be played - though this may not be possible, someone with more expertise will have to let us know.
I’d love to see krikzz take a stab at ODEs as well, but if he would prefer to only produce products that don’t require internal modifications - im sure if anyone can figure out a saturn flashcart through tje cartridge port he can - or partner with prof abrasive to launch the satiator like what happened with the sd2snes. The original playstation could be done but it looks like the ps-io may have that taken care of once they make their official launch. I wonder about if some sort of gamecube ODE/flashcart that would interface through one of the expansion connectors would be possible, or even a regular ODE as wasp, wode, wiikey, etc are hard to find these days. A proper jaguar cart has yet to be released and i hear it would be trivial to add jaguar cd support once a jaguar flashcart is up and running. I’d also like to see amore affordable neo geo AES cart - or even more exciting - an ODE for the neo geo CD that can speed up load times would be awesome but not sure it would be possible without removing and replacing the optical drive as a traditional ODE. And last but not least, my pc-fx with its ever aging laser could use some sd or usb based love.
As a side note, I sure wish we could get an update to the turbo everdrive firmware to add features that are present on the mega and N8 such as cheats, save states, the ability to hide the system folder, corrected sorting (my sorting is screwy on my turboed), etc - and even more importantly, if possible, the abiloty to act as an arcade card for arcade cd games (i guess super system 3 card support would be good for others, but i use a duo-r so only care about arcade card support).