Just when you thought you had enough dice in your bag ... Harley abuses his powers for evil.
Way, way back in the lost history of RPGs, a man named Louis Zocchi created the Zocchihedron, better know as the 100 sided die. I had the honor of meeting Lou at GenCon, where he gave me a bag of his dice --- though none that I could recognize. He's made d3, d5, d7, d16, d24, and 100, all statistically accurate. (Haven't tested that claim out myself. Buyers beware.)
Lou is something of a legend amongst the older designers. He shows up to all the conventions, but hasn't moved on to the web yet. To buy dice from Lou, you have to find Lou.
Sure, you're thinking, I'd love to help out a guy that was around when the first D&D booklets were being hand assembled in a basement in Lake Geneva. But what's the point? Some games call for a number in the 1-3 range, but I don't know of any that call for 1-5 or 1-7. ("What day of the week is it? "Roll 1d7!")
But wait. You and I write games.
Expect an adventure soon calling for a 1d7.