Joe, there are no wholesalers of bootlegs and "rare" concert DVDs (which are typically also unauthorised bootlegs) because the materials are basically black market. You want to sell dvd bootlegs, buy some, get a DVD burner and go to work. There's no one producing these things from a central location and reselling them to individual bootleg dealers -- in almost every first world country on the planet such an operation would be shut down for copyright infringement.
Authorised but rare videos, such as foreign releases and out of prints, are easier to source but there is again a very thin wholesale market -- check ads in Rolling Stone, Paste and other music industry magazines and you can generally find sellers of OOP/foreign release material. Contact a few and see if you can work out a wholesale deal.