I modified my printrbot GO with a door for the electronics (to allow access to the SD card primarily), so this is a latch I designed for it.
It is a parametric OpenSCAD model, so a great number of the design parameters can be tweaked to your liking and I imagine it could modified for a great number of other applications.
The STL is roughly appropriate for a 6-32 countersunk machine bolt and nut of approximately 5/8" length. I printed it out on my uncalibrated printer and still had to ream out out the hole for the screw considerably.
This is designed for a door that has a milled recess so that the door fits about 3 mm into the front panel, so you'll need to modify that if your door configuration is different. This can be modified with the offset (oFs) parameter.
Update: Adjusted SCAD to allow independent tweaking of offset parameter (distance of latch (lever) from panel) and adjusted STL to better approximate my situation.
I printed it out as the STL stands and with support and had to do considerably cleanup inside the nut trap - not great, but it worked.