Been sitting on this for a while, but now it's finally out:

A printable cartridge case for the Vectrex video game console.

The standard "Bottom" model is based on the design of the cartridge case used for the game "Rip Off" (ie. the black case in the images). The "Big Board Pins" version is based on the case of Richard Hutchinson's VecMulti flash cart (PCB shown in the last image). Note the "Rip Off" cartridge does fit in the "Big Board Pins" case.

Update, 23rd of May 2018:

I've added a couple of new case top designs ("switch hole") to suit one of the custom-programmed Vectrex cartridges that I have for sale at:
http://www.ombertech.com/vecrom.php

The hole in the top allows access to the game selector switch on the quad game cartridge.

I've also now tested the captive nut arrangement with the cart pictured and it seems to work well, though the nut had to be pressed in with some force using pliers.

Update, 7th of May 2017:

On request, I've made a new version of the top to suit securing the halves together using a captuve nut arrangement. It's sized to suit a 3mm nut and bolt, 1/8th inch might also work. A 25mm long bolt had to be cut down to 22mm so that it wouldn't stick out too far. "Top,_captive_nut.stl"

In response to another request, I also made a version with a hole for access to the SD card slot of the VecMulti multicart. "Top,_SD_Card_Slot.stl"

Finally, there's a version of the top with both of these modifications. "Top,_SD_Card_Slot,_captive_nut.stl"

I haven't tried printing any of these new versions myself yet, so print at your own risk.

I don't know if all original games are in "Rip Off" like cases or what other designs are out there. Also, this is very much a printable version of the cartridge case, not a very true representation of the original.

The text file is the measurements I made (mainly using a small ruler). The fact that the case works is little indication of the accuracy of these figures and in any case I doubt my strange terminology will make any sense to most sane people. Still it's up there just in case it's helpful.

I designed the models in an old program called Pro/Desktop that was a cut down version of Pro/Engineer (which is now called Creo, I think). The ".des" files are my design files in this program's custom format.

The prints pictured were made with a Makerbot Cupcake CNC. Yep, not everyone's moved on.

Oh, and sorry about the pictures, my digital camera is terrible.