I went to the local sex shop (the employee was surprised, but totally willing to help after she was sure I wasn't gonna be creepy) and only found one that would fit, since it was open-ended. The others were like 4 inches max, which doesn't allow for the satisfying thrust at the end. All the ones with any fancy features were in the hundreds of dollars, but were still limited in size. I ended up going with a $25 one that was basically a tube of textured silicone, open at the end for easier cleanup.

In short, go to a sex shop and look around :)