make any size you want out of brass tubing and some flat stock, and small hose barbs, like for water jackets.
solder tubing to flat stock, shape it.
drill hole for barb or vent/filler hole then solder other end with flat stock, shape.
drill for barb solder barb in ect.
solder a flatstock tab on to mount.
shape hose barb to fit stuffing tube and solder, drill out after. Presto!
Must have a hole drilled in oiler before soldering the second piece of flatstock to close up end of tube or it will build up pressure inside and push out solder,ect.
Paul