Buy the EZ Flash Omega or EZFlash Omega for playing GBA/GB/GBC/NES games, it's the best GBA flashcart with compatibility to all GBA/GBASP/NDS/NDSL consoles. It's also very cheap but with a list of powerful functions, such as Cheats, RTC, Real-time save and many other features. Just get one here with One Week Delivery from USA or FR.
EZ-FLASH Junior is a highly cost-effective GB/GBC flash card. It has features such as instant-load, real-time clock, upgradeable kernel and firmware, but the price is much cheaper. Supports all of the Gameboy systems including the Gameboy, Gameboy Color, Gameboy Advance, Gameboy Advance SP and the Gameboy Micro. Legit Official Reseller, Worldwide Shipping.