I made a non-captive one from a piece of aluminium rod and a file from Home Depot. Crude, but worked. New rods can be ordered from Italy (forget name of shop but if you search you'll find it).
If you know someone with a lathe I am sure you could make a nice one in no time at all; it's only the end that is keyed for the rubber buffer that needs work... I did it with a file in 5 minutes but looks rough, but worked great.