Portable Cart Flasher - BurnMaster
funnyplaying.com
Custom replaceable housing and compatibility with GBP button replacements Compatible with most self-made cart burning, reading, and writing operations Supports genuine card reading and archive writing 800mAh battery for portable power supply 1-inch OLED screen display for clear visuals Supports system upgrades Attentio

The Burnmaster is no available from their site, along with a MBC3 gbc cart and a 32MB GBA cart. The carts themselves looks like a decent value assuming they work with other writers but the flasher looks a little over priced to me since you have to purchase the case and buttons separately (total $30). The GBxCart RW seems like a better value unless portability and use without a computer a required.