If you've got access to a welder and some metal, then make your own bike rack, it can be a lot cheaper, and can be modified to suit your needs. Sorry I didn't take any pictures of the building process, hope you'll get the jist of how to build it and build your own. Enjoy.
Step 1: The beginning!
The first step is to take measurements.
1) Measure from the rack securing tabs to however high you want the rack to sit above the wheel, mine sits about 3in above the wheel. This will be your main support.
2)Decide how long and wide you want it. Mine is about a foot long by 4in.
3)Find your materials, for the main support I used half inch square stock, originally the whole thing was made of 8th inch rod, but it was to skimpy. All the supports are 8th inch rod, and there's a piece of mesh stuff on the top to keep pack straps from flying into the wheels, Pick your materials according to what you want out of your rack, and your tools, for example if you want an extremely light rack and don't have a welder use aluminum and bolt it together. In addition you'll need a hose clamp and a couple inches of half inch flat stock, if your attaching it the way I did. And of course you'll need nuts and bolts for the tab things. Anything else you think you'll need go ahead and grab it.