Take a look at pricewatch.com.
Go to cpu then to cases then to rack.
Here are some sample listings (not my recommendations):
KRI Computer CKS200 2U 4bay ATX Rack mount server case, 250w power $ 189
KRI Computer CK101B 1U 3bay black rack mount server case w/ ATX 180watt auto-sw power $190
Hardware Pro Black 19 inch Metal Chassis w/ ATX 150w $ 195
Hardware Pro EN-2100SX1R 19 rackmount Server Cases, 1U, one 3.5 1.44MB FDD,
1X5.25 CD-OM, 1X internal 3.5 HDD $ 225
P.S. Contact information and URLs are included as appropriate. Site prices are often higher, so must mention pricewatch. Shipping appeared reasonable, about $15 for the ones I checked. Have an understanding about shipping up front.