"SuperRetroBoy: A 3-in-1 handheld, single port gaming system that instantly plays classic Game Boy, GB Color, and GB Advance games."
I'm totally with you ... I think the GBA SP with the bright screen is a high bar to clear. I love its small size, perfect controls, fold-up screen, and long battery life. It also plays every GB, GBC, and GBA game. What I don't love about it: nonstandard charging and headphone jacks, plus the fact that they don't make it anymore.
A clone will have to be significantly better than the Revo K101, which fixes the original's issues with nonstandard charging and audio ports, and adds the ability to bring your own games. I'll bet it will be somewhat worse, but cheaper than the going rate of $110.
The flavor-of-the-month seems to be the GB Boy Colour, with its off (though not by much) sound and slightly misshapen screen. I'm not going to spend any money on a system that can't even get the shape of the screen right. I won't lie, I would spend some cash on a "new" Gameboy, but it better feel like I'm picking up something Nintendo themselves made.
There's a booming market in GBA refurbs. If I can get the real thing for under $100, which I can, Retro-Bit has zero room to screw up.