Roll Pin MIA

I was wondering why my Dart was all wandering over the place. I was diagonosing it today and my roll pin is gone. I have seen lots of posts about trying to get them out I didn't have that problem. Can anyone tell me what size it is for a 74 Dart (looks to be around a 1/4"). Are they readily available and for the guys North of the 49th have you found them in Canada?

Thanks

Mike