I have the Anbernic rg351v and really love it for SNES, GBA and NES games. I can play N64 games but without the C buttons it's harder. Great for arcade and rpg style games like Zelda and Secret of Mana, etc. I haven't used it in awhile since I got a steam deck, but is a solid device in my opinion. Should be able to find around $100.

There are better ones that are landscape, larger screen, dual sticks, but for retro stuff I wanted as close to Gameboy form factor as possible