>>713537073 (OP)If size is a concern like that, I'd say either a non-XL N3DS or a small chinkheld off aliexpress. Probably one of the RG35XX models or the TrimUI Brick or something. They'll only emulate up to PS1 games, but most games past that aren't terribly great on small 4x3 screens anyway. Don't be afraid of the vertical/gameboy layout devices, they're more comfortable than you'd think and do a lot for portability. Something about them also just gives off less autism vibes if you're at all in public.
Possibly you could go for a Retroid Pocket style device (idc too much about those so I don't know if there's better options than the Retroid Pocket 5 itself), which are a few hundred and can be about the size of a large phone. I feel that class of device has largely replaced the PSP/Vita.