RPF1's would be awesome to have, apparently there are sets floating around with the 5x108 bolt pattern, but I've only seen one show up on eBay.
Sparco Asseto Gara's are still probably going to be your best bet for something lightweight and not overly expensive. They are 19lbs ea. for the 17's and 21lbs ea. for the 18's. 18" O.Z. Ultraleggera's are 18.5lbs ea. as well.
I agree though, our options for wheels is really limited.