GB Smart 16M
GB Smart 16M - 2MB
Allows multiple games but they must be aligned correctly for them to boot.
GBxCart RW - Multi-game Maker
Drag and drop your rom files to GB_Smart_16M_Multi-Game_Maker_v1.0\multi-game_maker_v1.0.exe file and it will just create an output.gb file if one doesn’t exist. You can keep doing that until you hit the maximum of 2MB. It's best to drag and drop your smallest rom files first as each rom file has to be aligned so larger files will waste free space.