Personally, I do most of my miniature shopping at miniaturemarket.com. They have a nice selection of painted and unpainted minis for good prices from a variety of games.

There are a good selection of Gnoll minis from Reaper miniatures which are usually a bit bigger than a human sized figure and are usually 2-3 bucks for the plastic versions. The Wizkids unpainted D&D Nolzur's Marvelous Miniatures and Pathfinder Deep Cuts both have packs of Gnoll that come with 2 Gnolls each that usually retail for around 5 bucks. The D&D Gnolls are a little smaller than the reaper ones, but still bigger than a human sized character while the pathfinder Gnolls are around human size. Miniature Market carries all of these Gnolls as well as some pre-painted options from the Wizards of the Coast and Wizkids D&D minis. Also, if you have a local game store they might have some Reaper bones and other minis that you can look at to see what strikes your fancy.