Most stucco/plaster patterns/textures aren't/weren't created by any particular tools but rather by incredibly highly skilled craftsmen. In otherwords, the pattern was created via decades of experience and skills rather than a particular tool.
We have a stucco house and over the years I've talked to a few contractors and they all same the same thing...good luck finding anyone still alive that knows the particular texture we have on our house.
I eventually had to patch part of it myself. Fortunately, it's on the side of the house few people see. ;)
That said, here's an idea:
You can purchase silicone mold forming material (often used for replicating architectural plaster mouldings and ornamentation). You could purchase some of that and make a cast of maybe a 2'x2' area. Once the mold form is created, patch the area you need to patch with a sloppy-ish mix of stucco. Apply the mold on top of that, let sit, then remove.
It's a long shot, but maybe any option.
Barring all of that, get some plywood, get some stucco, and start practicing. See if you can replicate it.