The provided STL mesh is for a set of Zarruchi Z04 lenses with an IPD of 63mm. That link is a web archive link, since the product is no longer available on the site. The lens height is 39mm and width is 52mm.
Used jegstad's design as a basis for the outer frame/holder by redoing it in FreeCAD and ensuring dimensions matched (i.e didn't end up using the same mesh), except I made some changes to the 'fingers' at the bottom.
I was playing around with the new expression-constraint features in FreeCAD 0.16, by linking to a set of internal spreadsheets. It should be possible to adjust the values to produce a new printable model that will fit sufficiently tightly around other pillowed-rectangle shaped lenses. Maybe an old pair of prescription lenses could be used. My primary reason for uploading is that someone else may find the measurements for the outer frame in the freecad model useful.
If you do try to use this design however, I suggest adjusting the values in the "LH" and "LENS" spreadsheets. The "UC" spreadsheet controls the outer shape and shouldn't need to be adjusted. Then cut out everything but one of the central 'holder' parts, and print that out until it fits.
Warning: this puts the lenses very close to the rift's own Fresnel lenses (at least for my prescription), so be careful!
Note: The photos are actually a slightly earlier revision, also my final print was in black PLA, not green.