I think your gonna find your best deals on ebay. When I was building my cnc plasma table a few years back, I did a lot of shopping around, and I found some rails with the bearings, used for a very good price. There are a lot of vendors that resell this used syuff on ebay. Shop around and be a little patient. There's also vendors that sell new chineese stuff too, for very reasonable prices. This is an area where american made can be triple the cost.
Marcel