Hi Jessica;
I always made my own patterns for guns, tracing around the outside being sure to leave extra for the filler strip along the edge.
Make it out of paper, you can make several patterns if you need in order to get the pattern you settle on.
The first one you make in all likelihood won't be perfect so don't expect it to be, just take your time and do the best you can.
Perfection comes with practice and you can always improve the results.
Look at all the holsters posted on this site for ideas.
Kevin