To my knowledge, there are 3 types of pins: roll (or "coiled"), C-type (aka "spring pins") and solid dowel pins. Then there are variations on each of those. In plastic, you'd want to use the C-type or dowel pin because the plastic can't take the stress of compressing a true "roll" or "coiled" pin.
These pins are sold everywhere, including industrial supply houses, home improvement stores and good hardware stores. They are defined by their Metric diameter and Metric length. Example: 3mm x 18.
If you want to change the grip often I would suggest the
solid dowel pin, which has a
generous radius on one end. The other 2 types fit so tightly as to push out a small amount of material with every fitting, eventually rendering the hole over-sized and therefore useless.
Check out McMaster-Carr's selection
HERE.
There are also special drift punches sold for removing and replacing the 2 types of hollow pins.