I think UM quit making the sling kits, can't find them anywhere except a few on ebay once and a while.
Bullberry makes them out of replacement hex head bolts with the short machine stud silver soldered in the hex hole. For the Contender I just added a machine stud to the grip cap. This works on wood and composite caps but not the rubber grip. Screw style stud work on the wood grip.Use a thick spacer or the bolt will bend under pressure.
For my Encore i made my own using a hex bolt with stud added and a spacer. I drilled and tapped the bolt head and loctited the stud. Soldered machine stud in hex bolt works also.The spacer I used pressure fit the grip making it solid and not letting the bolt bend.
The G2 is not like the origional Contender. G2 and encore use the same . Wood grips I would just use the screw type stud.I just left the cap off. If you instll cap you will need a longer bolt and need todrill hole in cap so stud fits thru.
Pic 1- contender with machine stud in grip cap
pic-2 cap with machine stud and nut
pic 3 Encore grip with home build stud
pic 4 stock bolt, bolt with stud added, machine bolt, hex head bolt , spacer , machine stud and screw stud. Spacer is 3/4" x 5/8" and pressure fit into composite grip. Works on both encore and G2.
Hope this helps. maybe Mark or quick2do could sticky this so it is easy to find.