I am looking for some sort of clip on barb that will clip onto the shaft of a hook to keep jig trailers from sliding down.  I'm not sure there is anything out there but it seems simple enough that there would be some sort of solution.

I think you can get what you are looking for at Netcraft. They're called "Hitchhikers" and are on pg. 48 of their 2009 Catalog.

www.jannsnetcraft.com

almost, but not quite.  I think these would work good for finesse jigs though. Thanks for the link.