Here's the stereo bar kit I got with my matched pair of Microtech Gefell M300's. Supplied with a transparency overlay with all the correct angles and measurements on it so setting up for ORTF is a breeze.
I don't know if they sell it separately (and MG spares are notoriously expensive) but it's an extremely well engineered piece of kit - miles better than several cheaper stereo bars I've owned.
As other slutz have pointed out you need a sort of spacer (visible on one mic clip below) in order to raise one mic's height and thus be able to get the capsules to really overlap correctly for XY and ORTF. As a point of interest what is this little widget called - can we start a naming contest?