All you need are some laser modules, which you can get here:
dx.com/p/6mm-5mw-red-laser-module-3-5-4-5v-13378

and some button cell batteries. I used some cheap standard LR44, which I got a 30 pack for about 2 bucks from a hardware. The whole assembly shouldn't cost much more that a buck.

Simply print, and remove the built in support around the battery stack (should just break off when you press it, or you can use an exacto knife). Just pull the wires of the laser through and strip the insulation, so that one contact is at the front of the stack and the other at the end. Boom. Laser ring.

The reason my lasers have a whole bunch of dots is that i slipped in a little bit of defraction grating, which is a trick i pulled from here: instructables.com/id/Laser-Ball/step4/Diffraction-grating/

Its cool, but not sticktly necissary. You can get some from ebay, or here:
scientificsonline.com/holographic-diffraction-grating-film-10036.html?&cm_mmc=Mercent-_-Google-_-NULL-_-3054509&mr:trackingCode=736F1735-DB81-DE11-8C0A-000423C27502&mr:referralID=NA