Attaching a base to a "Clone Your Willy" mold

I know nothing, so be gentle: I made a mold of myself that turned out really well, but it stops at the end of the shaft. I'd like to attach a flare, or base to it but have no idea how to go about doing this.

Obviously the one I made is long-since cured and dry... If you have a moment to describe the materials I need etc. or a good link I'd be grateful.

I was thinking I would even just buy something from the Love Shoppe that had a base, and use that (cutting/pasting)? Is that feasible?