The cars are still called Sizzlers and are only available at Target in store not online
However you can get them on ebay pretty easily too as well as some of the vintage cars.
SizzlerKing's website is probably the best with information and has links to other sites with good information as well his site is here
http://www.geocities.com/baja/trails/6896/indexa.html
He actually answers emails and this is where I found out about the new Sizzlers. Make sure you look at everything on this site there is alot of information on just about all the history of Sizzlers.
My problem is the lack of technical information on these great cars. SizzlerKing has pictures of just about every car and track setup. I never realised that there were that many track layouts available. You can find Fat Track sets on ebay too.
I also think everyone here will be interested in the way the cars charge. Go to SizzlerKing's site he explains it way better than I ever could.
If we can find r/c cars that will work on the Fat Track setups we can figure out some of the limitations together and perhaps find someone to fabricate track mods as the only really useful track parts available are the banked turns and straight sections. I'd personally like to see some flat turns, hair-pin turns, esses and chicane sections like the ones that are available for slot cars.
Mattel also made cars called X-V Racers that have been proven to work on Fat Tracks, but like the Sizzlers you can only charge them and let them fly on the track. From what I have read they don't take as long to charge and don't run as long. These have been discontinued.
I was in Wal-Mart the other day and saw another Hot Wheels car that may work on the Fat Track too. Turbo Glo's. The are more similar to X-V Racers and appear to have the speed needed to make it around the Fat Track as well. I will pick one up and let you know how it works out. I also saw these at K-Mart.