from the parts manual it looks like a lot of Williams games use " C-6520" wiper
http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1971-1972/index.html#/147/zoomed
http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1971-1972/index.html#/15/zoomed
call Steve Young @ pinball resource maybe