I have a few cars with bizarre wiper sizes and assemblies and I've had to get creative in finding reasonably affordable replacements. What I've done is measured the length of the wiper rubber and gone out and purchased high-quality replacement inserts that are one size bigger (unless I could find the actual insert size). Then you remove the whole original assembly from the car, disassemble it to remove the insert, take the stainless steel side-rails out of the rubber insert, cut the new insert to the right size, insert the stainless rails into the new insert, and reassemble. It's a bit of a pain, but really not that bad when you consider the inserts are about $10 a pair for top-of-the-line products and a pair of replacement assemblies is about $120.
Another side benefit of going this route is you aren't wasting the old assembly. I think it's kind of a shame to throw away a perfectly good assembly just because the rubber blade wore out.
EDIT: One other thing, anytime you change your wiper blades, either put a big rolled up towel on the base of your windshield or make sure you carefully lower the empty wiper arms back down to your windshield after you've removed the blade assembly. I can't count how many times I've heard people cuss because they were doing what they thought was an easy money-saving job and they let the wiper arm thwack up against the windshild and it all of a sudden got really expensive.
