You can make a mould so u can make several easily.
First you will need to make a "plug" basically the shape of what u want but solid, out of foam or wood, MDF`s good for it. The smother you can make the plug the better because ay imerfections here will shw on every one u make
Second you take your mould off of the plug, using lots of reinforcements, so when u doing the moulding of the bit u want it wont warp.

Hope it helps