Truvativ don't list any other track chainrings on their website so I'm guessing the 48 is the only one they do for now. The Omnium crank is pretty new.
Plenty of other good track chainrings out. All are pretty nice. You pay a premium for finish, logos etc but unless you're a world class sprinter I doubt you'll see any difference.
In the budget category Sugino make very decent track rings, as do Gebhardt, FSA etc. Theres also plenty of NOS/2nd stuff out there and you can often pick up the high level Sugino, DA, Campy and Suntour stuff for a decent price.
Nice thing about track chainrings is that they last a long time so its worth investing some money in them.