All good ideas and the last point may be an overstatement. My understanding is that most of the smaller bike shops opperate on a shoestring and probably don't have a large credit established with distributors and such. The larger ones Performance etc. are big enough to get almost anything they want FAST because the do so much business with their suppliers.

If it were me I would say to the LBS, "Look, I have waited a long time. What are you prepared to do to make good on this sale?" If you want "training wheels" ASK! If you want a comperable wheel, ASK! If you can be patient, let the Owner of the LBS know you are going to wait (and how long) and see what he is willing to do in the way of giving you free services or other stuff you need (that won't bankrupt him).

The other question that occured to me is this:

Why can't he get a set from another shop in the area?? Most of these guys know each other well and he probably could get them if he asked (and that way you wouldn't be forced to do the shopping). Have you asked him to see if he can locase a set from someone other than Mavic??