Haven't called Sig yet, but I did check their website and didn't find anything. I know Greyguns makes them, but they seem to be sold out, always.
My problem is the spring is so tight against the flat end of the rod that I can't get it off by hand. I'm afraid if I try and grip it with anything else I'm going to snap it. I'm sure it's way more durable than it looks, just not sure if I want to chance it.