While it may not be convenient...the time, materials and practice it will take to make a good one...or even a good enough one from scratch is probably a lot more than making one. If you have to ask how, then you've never done silicone or soft rubber molding. That in itself takes practice. Order one on line. It will cost a quarter or less than learning how to do it yourself.

UNLESS! You have access to a VERY exceptional pussy to duplicate and can sell copies. Then...maybe.