For example https://patents.google.com/patent/US9311738 or https://patents.google.com/patent/US7432937. The second patent mentions an alpha buffer which has stencil buffer operations instead of a stencil buffer, not sure if it matters how the thing is called. Although the second patent could maybe be worked around by incrementing the alpha buffer instead of toggling it. This would fail with polygons with a winding number higher than 256 (or 2^23 with 32 bit floating point), so good enough for almost all applications.

Several other patents can be found when searching for "patent stencil polygon", but I don't know if they are relevant or not.