As a novice in this field I may be wrong ( and happy to be corrected ) the plugs I have bought for my 1918 and my 1925 engine are NGK dpr8ea-9 plugs. It cost me about 10 dollars australian. Unsure as to wether they fit your model.
the leads I obtained from "vintage wiring harness" in ringwood , victoia , australia.
Hope this all helps and is not too wide of the mark
regards michael