Take a piece of foam pipe insulation for 1/2" pipe. Open it lengthwise and roll it into a tight coil. Bevel the top a little with scissors, then roll a condom down over it. I use one of these to suck on, pretending it was a cock. It is about 5" around, make it as long as you want.
If you want it stiffer, say for fucking yourself, put a piece of dowel down the middle of it.