Tremec roll pin

[HSSS427]

Lost first and second gear today on my TR-3550. Found that the roll pin holding the first-second shift fork to the shift rail had come out. Dumb question is - where do I get the correct roll-pin? Are these just off the shelf hardware items from Home Depot or are they special and specific for transmission use? Also, since the pin is gone, I'm assuming the magnet in the bottom of the pan will pick it up, or do I need to drain the pan and go fishing? Also, if it's an off the shelf item, how do I best determine the diameter and length of the pin?
Thanks!
Scott

[HSSS427]

I called the Tremec distributor and he gave me the dimensions of the pin (.2 x 1"). Found a 3/16 x 1" at the Ace Hardware and knocked it in. Seemed to fit just fine, but haven't driven it yet. The big pain is having to take the seats, carpet and tunnel out to get at the thing. Also managed to fish out the old pin from the bottom of the pan with a retriever magnet. Wonder what will be next on the list of things to fix