Well, I've found another option:
http://www.superiorpod.com
Again, they print Poker (or Bridge) size cards but this time, they seem to be saying that they can guarantee registration for the face side (they suggest a full bleed pattern on the back side). There is a minimum order of 3 packs but the price doesn't seem bad. I'm not sure of their marketing arrangements if you want to sell through them but for a small print run for you to sell yourself, it could be a runner.
Although the tuck boxes are for a couple of standard packs, there is a suggestion on the pricing page that for a one time set up charge they can produce custom sizes - if I've understood correctly, then they may also be able to print a LWB to enclose with the pack.