1/2A kits in general are hard to come by. I pick them up whenever I find them and convert them to electric but WWI is even harder to find.
However, Airage has a lot of plans for the old bipes, a few in 1/2A and several in 40 size. I have built the SE5-A and D-VII. As designed they are a bit heavy but can be lightened up, A LOT!! The wing spans on the 40 size is under 50 inches. I do see a couple of Stearmens in 1/2A, the 17 and the 13D. Even a DH2. Plans can be reduced to any size you like. I gave away all the plans I have for them or I would have sent you some. Cutting your own kit is really easy, a lot easier then locating the kits.