I've never seen one of those in person, only in magazines. Easy enough to make, the only tricky bit is attaching it to the marker. Naturally the grip frame will have to be drilled and tapped (I'm assuming) and we'll have to figure out how the "lock" works, if there is one. (To keep it from collapsing when extended.)
I can envision a couple of ways to do it, but if you can find a pic or reference of how the original worked, it'd help.