Seagate has switched to 5400rpm hard drive mechanisms and renamed their hybrids SSHDs. There's a 500GB, 7mm and a 1TB, 9.5mm version. The 750 GB, 7200 rpm XT is still in stock in some places.
A fusion drive requires a model that is running Mountain Lion and has room for two hard drives. With a C2D MacBook(Pro) you'd have to do the math to decide whether it's worth it to buy the two drives plus the kit to convert the optical drive bay to accommodate your HD or SSD, and the time/$ to do the surgery.