Quick and easy Dynafit modification.

Bought them at Hardware Sales, Bellingham. They are fully threaded.

I did a field repair with an 8d or 10d [ETA: can't remember which] nail.  It was a few years ago and AFAIK the nail is still in the guy's binding. 

Is there another name for a "threaded pin"? It seems like a shoulder bolt or something unthreaded through the binding would be optimal, but I can't trivially find a 3mm shoulder bolt.

Toby used what is typically called a socket head cap [machine] screw.  I agree that the right dimension shoulder bolt would be the better hardware, but it might be tough to find one just the right size. 

Sorry, I didn't realize you were quoting my "threaded pin" description until I re-read my post. Steve is right on with the description. I just went in there and asked for 3mm replacements and they offered up a Grade 8. Works great. Fits perfect. If anyone has a 3mm "shoulder bolt" it would be HW Sales... at least in Bellingham. Maybe give them a call?
I guess if you really wanted to get technical about it, a Grade 5 may have more preferable failing qualities vs. a Grade 8 in this situation. But, here I thought Grade 8 3mm was an oxymoron of sorts

Either Grade 8 or Grade 5 will work for this application.  Hell, a nail has worked in my bud's binding for several years.  The shear forces aren't very big on this pin.

I haven't seen this problem (pin slipping out) on the newer Dynafit toes, i.e., the ones with the cutout and beefier pin socket.