You may have already sorted this but many years
ago I bought a POLAROID radio remote (once used on their topline Spectra cameras) and wired it to
the remote cable for an ELM.
It worked extremely well. I would imagine one
could do the same with the Release cord 3054510
(all you really need is the plug to fit the into camera)
There is a gentleman on Ebay who provides these radio units "rewired" routinely. I don't know if they would work on the XPan or not never having tried it. He might be able to tell you if it would work however.