I was never a big fan of the Gameboy Advance so I don’t have any cartridges lying around. But if I did, I would be turning them into flash drives, just like this one from etsy seller 8BitMemory. That cartridge above looks awesome as a functional USB flash drive.
Currently 8bit has several for sale including Metroid, Super Mario Advance, and Mario Vs. Donkey Kong. All the converted cartridges have a 4GB capacity and they retail for $39.99 each.