Loose PS2 tray

I picked up a used Fat PS2 with a loose tray, upon close inspection the disc tray guide nubs (two of three) that the tray rides on have broken off. Any ideas on what could be done to replace the broken nubs with something equivalent that is practical, not looking to replace the entire drive as it works. Thanks in advance.

Here are the photos of what I'm talking about, photo with red circles refer to the broken nubs
http://photos.app.goo.gl/soLAdaCWbNGS28u57....

Loose PS2 tray