hopefully best quality is from C & C as ive just bought a full set of delux german quality seals at the weekend which i will be fitting before Brighton so will let you know :!: :!:, saved £90 with ordering and collecting at Busfest
C&C seals are good, the vent seals aren't as good as nos or WCM though. Have seen a nos one for sale for €100 somewhere, vintage vans I think, based in Portugal.
http://www.vintagevans.com/pt" onclick="window.open(this.href);return false; is the sight, got some nos brake switch boots from him, very happy with them, he's on the samba too with good feedback. Hope it helps