Looks to me very much those two pink items are 'Heat Shrink Wrapping' - the stuff you put over items to insulate them and then apply gentle heat with a heat gun or whatever and it shinks down to the appropriate size!
To be honest it all looks a bit Heath Robinson and not a little dangerous as well.
The only way I can see that working would be to wrap them around existing rubber grips, using something like tape or a rubber band to keep them in place, slide the heat shrink tubing over the whole lot and then shrink into place! Very dodgy as HST is really designed for the constant abrasion it will be getting from you gloved hands..........
I really do hope it was as cheap as you say, because I'd chalk this one up to experience, chuck the whole lot in the parts bin and get something that actually looks like it was designed to go on a motorcycle and not knocked up on during a junior school craft and design lesson LOL
P.S. What 'other' Forum????