Otona no Kagaku #25 with Gakkenflex TLR brand_Lensmate this Canon Powershot A550 might

this Canon Powershot A550 might do the trick

Interior dimensions are approximately 10x17x20cm

and compatibility with any Pentax K-mount lens

and I think there's more potential here than that

Otona no Kagaku #25 with Gakkenflex TLR brand_Lensmate this Canon Powershot A550 mightThis is issue #25 of Otona no Kagaku ("Science for adults") magazine, featuring a fun little comic strip about virus transmission (topical!) and plenty of camera information plus, of course, the famous Gakkenflex 35mm TLR kit, complete and unassembled. If you can read Japanese, you might get a kick out of the magazine; if not, you can always just assemble the camera and have fun with that.