We have cat lazer lights that they fit in but the light quality changed, it widened. We took it out of an old pump because I wanted to see what the insides were like 
I don't think they are real expensive at the office supply anyway and they come 500 in a box. Pribably could reuse them if you get a few at your doctors office too. Great if that is your biggest problem huh? LOL.
I love your investigative spirit!