Looks like there are 3 models, a super-tiny 3-button handheld with some standard Sega games built-in, a larger 6-button handheld with cartridge slot, and a console unit with cartridge slot and SD slot

The 6-button handheld is on sale for CAD$45, but I really ought to be saving my money for now...
edit: unfortunately I should add, the D-pads look ass on those handhelds (especially the 6-button one).