Sure grips can be found in performance cars, trucks, vans, etc. so you have to look for them. There are two types of suregrips, cone and clutch. The clutch type, Dana "Power - Lok" came in the earlier 657, 741 and 742 carriers from 62 - 69 and is rebuildable. The MP rebuild kit for this type of SG is PN# P4529484 and it consists of new clutch disks and plates.
The later cone type suregrip commonly found in 489 carriers was produced by Auburn Gear before Borg Warner bought them out. It is called the Borg Warner "Spin - Resistant". It has a bunch of springs you can see looking in from the side of it.