If you have decent flat art, like a profile and plan view in the instructions, making your own is pretty simple.
I make several photocopies at scale, and be sure and check that against the model as it may not be.
Put down some low tack (orange core) blue tape on the cutting mat wide enough to make a stencil from.
Tape the copy down over that. Usually I'll trim the copy fairly close to the edge of the aircraft, then tape all around the edges.
Cut out the stencil with a sharp knife.