This set has been on the market for a while, not sure if you’ve seen them or not. They definitely need some work, and aren’t the exact offsets you’re looking for, but are close. Maybe the seller is negotiable now that they’ve been for sale for almost a year...
https://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/978031-fs-fuchs-wheels-widened-9x15-11x15.html