This is a improved version of my former design. The inner diameter has been decreased to improve the clamp strength onto the handle bar, the outer diameter has been decreased as well as a change in the grip pattern to improve ergonomics. Additionally, this design also incorporates a small groove on the inner portion of the grip to allow application of safety wire to increase the interface between the grip and the bar and further prevent the grip from spinning during its lifetime .

How to make the grip using the mold:
Print all three parts of the mold, and purchase a castable silicone. There are many offerings from Smooth-On, which can be purchased from Amazon. My grips used a Smooth-On MoldMax 40, which worked well. Furthermore, to improve tear strength Kevlar pulp can be added to the silicone during the mixing process.

For step by step directions, MakerBot created a great video which can be seen here:
https://www.makerbot.com/professionals/post-processing/silicone-molding-2/

NOTE: Mold release agent does not need to be used, as silicone will have a tough time adhering to the mold.