Psh the Sega Nomad is where it was at, *** that Game Gear noise.
Talk about eating batteries, and the screen was ***, thought it was a full on mini crt, but I can't find documentation that backs that up, so I'll scrap the idea for now. There are TFT LCD replacements that can be done, and even rechargable pack upgrades to do something along the lines of making it microusb rechargable, but I'd probably just replace the screen and fix my 12v input plug and get a replacement battery pack and use higher end rechargable batteries, I may con myself into using a 2nd pack and modding that with a higher capacity battery and recharging circuit.
Looks like the Nomad used 6 AA batteries, so 9v, or took a rechargable pack that was rated at 1600mAH, there's much better options now, and looks like that output 7.4v, simple enough to do if you shop around for the right parts.