Interesting. With Plastruct no longer supplying clear, we're sort of hosed. In a quick scan of suppliers,
Tap Plastics has 1/16" and 1/8". I use Tap a lot, maybe a bit expensive but they always have what I need.
In searching I found a site with fiber optics in metric sizes,
http://thefiberopticstore.com/. Site is a little retro but they seem to stock a variety. 3/32" would be 2.4mm, and unfortunately they show only 2.0 and 3.0mm.
If it were me I'd take the closest size up, chuck it in a drill and turn it down. Not the best thing to do in terms of light transmission, but if the distance is short it might get the needed result.