To comment on the SD shield, I have one made by @kennethlimcp, in the same form factor as the Particle devices. I’m not sure if he has more of them, but I’ll leave that to him to answer.
@futurebird, I now have an RGB Matrix Shield PCB and parts kit available for driving Adafruit 16x32 and 32x32 RGB Matrix Panels. It plugs into the back of the panel and can drive multiple panels. It is very new and I will be offering on Tindie after I offer to Community members directly. Here is a view of the board:
it works really well, im about to share a balancing robot project using it once i have time to tune the PID and actually get it standing by itself (it kinda does but oscillates badly). I'm not selling it, but feel free to make your own boards etc. all the parts are in the BOM