This is a portable Rasberry Pi in a case that might look very familiar if you've ever seen the Famicom-themed GBA Micro. It isn't cheap, but it's a neat device, with an interesting concept.
Waveshare GPM 280 on Amazon (Affiliate):
Too many handhelds is a video series that takes a look at a variety of handheld video game systems. These are unscripted, informal reviews of each system, going over the pros and cons of each.