Here's a PAIR for USD 140.00 which I found on a quick search for "centerlock 29r rear wheel".
If you rephrase your search a few ways you should be able to find more choices. Also keep in mind that a 29r and 700c wheel are really the same size, except that one is marketed to a mtb audience, and the other for road. Ther may be functional differences, but search both and read the specs since a 700c touring/cyclocross wheel may be just the thing.