Your best bet is to get firmware updates from the website printed on the card's packaging, usually all the various R4 clones use cracked R4i Gold software/firmware updates though some never bother to update their card at all.

But if they dropped support entirely there's not much you can do.
You can certainly try to update the firmware but you risk bricking your flash cart.

Currently the R4i Gold 3DS is the best R4 clone out there that gets regular compatibility updates. I've never had an issue with mine except for incorrectly formatting my micro SD card, but that was my fault.

This post has been edited by Monty Kensicle, Sun, August 25th, 2013 at 08:52