If there aren't any on this site, try the vet resources on other sites: Glider Central, the Sweet Spot, etc.
If those don't turn up any, here is a general exotic vet listing:
http://www.aemv.org/vetlist.cfm
Be sure to ask the vets lots of questions to ensure they're able and willing to care for your glider:
http://www.glidercentral.net/ubbthreads/ubbthreads.php?ubb=choosing_a_vet
It might be worth it to travel a few hours to a more experienced, less expensive vet to get the boys neutered, so that is another thing to consider.