Man, normally I'm great at figuring something like this out but I've completely struck out. Scottosan, maybe the reason the VoodooAmps are all pictured with chicken head knobs now, is their supplier quit making these single 0-ring w/indicator knobs? Unless you find them, I'd just contact them and tell them you're missing a few on 1 of their amps and see if they still have any to sell you?
Eric