Grenadier later produced this Demogorgon look-alike but called him Orcus for some unfathomable reason. The head is reptilian instead of baboonish, but it's still pretty neat-o. I have one of these I bought off the eBay, thinking I was getting the Minifig version. Here's a link to a nicely painted version of this figure.
The Aspect of Demogorgon from Wizard's plastic figure line. I like the concept of buying a prepainted Prince of Demons, but the sculpt is too thin and spindly, lacking the look of raw power in the earlier versions.
Reaper's Dark Heaven Legends line has a lot of great figures designed for D&D play. This fantastic fella is called the Demonic Lasher in their catalog. They like to file the serial numbers off, don't you know. On this page you can find a great painted version of this figure.
New Book - It folds, so you can page through it or spread it out as needed.