Here is a source that I and other bat rehabilitators have used to buy bat flight cage netting: http://www.industrialnetting.com/pest.htm#bird  Scroll down towards the bottom of the page under Bat Control Net, and look for 1/6", #OV 7100. The mesh is tight enough that bats can’t get out and can’t get tangled up, but large enough that some insects can get in to give the bats some bug-hunting practice before release back to the wild. You might also want to tell your friend about the bat rehabbers newsgroup, WorldBatLine,  http://groups.yahoo.com/group/worldbatline, that was founded by the head of Bat World Sanctuary. The group has experienced bat rehabbers, bat rehab newbies, other critter rehabbers who get in the occasional bat, and folks who are just interested in bat conservation.

Thanks for wanting to help your friend help bats! ^..^
cindy m.
www.BatWorld.org