This is a case for the Krikzz MD Flashkit Programmer.

Cartridge Connector slot is supported so as to not bend the PCB when inserting the Flashkit. Have only tested it with PAL cartridges.

Print with the top half upside down to reduce the amount of required supports. See the Simplify3D image above where the supports should go.

It's a snug fit, but there is space for 4 M3x10mm screws to really secure it.