The ones used on the FP-rear needle vale series, both R/C and C/L versions, used that needle. The needle valve assemble was mounted to a metal bracket held on with the rear cover plate screws. The NVA for the carbs you have screwed into the carb body, a 4mm fine thread I believe. I use these NVAs for spigot style venturls for control stunt applications. I think they are quite universal among a wide range of OS engines starting with the MAX series up to the FP series. That may help your search. You may have one in a junk box and not even know it! Looks like you have had a good response to your post so you should be fixed up.
HAPPY HOLIDAYS!
Dan McEntee