For my C8 build, I bought most of my RS parts from Brownells. They do sell the small diameter CAR grips, as well as the full length A2 type. I picked up my C8 grips for about $18, $5 shipping, and the entire package was on my doorstep in Toronto in two days.
http://www.brownells.com/.aspx/pid=5...UND-HANDGUARDS
These are the grips you are looking for.