"But isn't Papias a bit of a shaky source?"
What source isn't going back that far?:)  I suspect any two historians will argue three positions on Caesars' The Gallic Wars.
In total, I think that is possibly true, but a lot of what Papias is supposed to have said come to us as quotes or references via other authors - Origen suffers the same fate.  Regarding Luke's account, Papias' shorter account (there are actually two; the longer as a comment on Matthew and the shorter on Acts, if I recall) of Judas' death seems to be the more authoritative.  The longer account (much more graphic), seems to have been somewhat "expounded upon".  Luke was clearly aware of the story that Judas survived the initial hanging (probably his readers were, as well) but chose not to dwell on that subject since it wasn't even a secondary consideration in the scene from Acts.