Chasman, there is a spring steel half moon oval washer between the peg pivot and the peg square boss that tensions the assembly and gives the peg the "over-center latching feel". The peg mounting pin assy is $12 for a pair (in chrome).
HD also make a "Bullet Chrome" nut and bolt kit if you want to tension the assembly tighter if you do not use it that often for the same price. If you want to go "simple" you can use a thin metal shim washer out of brass or copper to wedge in between.