I couldn't find any add-on boards either!
I built my own add on board using the chips mentioned above. There is alot of information out there regarding camera link. I do not think it would be too hard to build what basically is a frame-grabber on the FPGA.
I only did this one way, I did not have to provide any camera control signals (CC1, CC2, CC3, CC4, serTC etc) as I still used a PCI framegrabber. I just provided the FPGA with the camera link outputs (x0+, x0-, x1+,x1- etc), via the chip DS90CR288A (camera link reciever), aswell as the timing signals this provides (FVAL, LVAL, DVAL) . You would need to use the camera link transmitter chip if you want a stand-alone system.
I used the high speed expansion connector on the xupv2p, I got some connectors direct from the manuafacturer Hirose. Here you are provided with ground and power, and have 40 (I think) i/o's to play with.
Some people have tried to perfrom the LVDS deserialization on the FPGA, but make life easy - use the dedicated IC's! I found this document quite useful, there's some schematics towards the back.
http://www.latticesemi.com/documents/TN1134.pdf?jsessionid=ba30ba2f959f$84$0A$9