You can pick a used one up for pretty cheap. Add a flash cartridge and you're done. I think the cheap android handhelds of the same form factor are a better option though.

I've still got my Gameboy collection, but rarely use it. It's just so much easier to fire up an emulator these days.

You can buy the ModRetro Chromatic from the Oculus VR creator. It's better than anything Nintendo could ever produce.