The extenders might not be for this specific carpet kicker but it does the trick.
Roberts Knee Kicker Carpet Stretcher 10–412 Adjustable Teeth, Tool Length 17"
Roberts Knee Kicker Carpet Stretcher 10–412 Adjustable Teeth Tool Length GUC
ROBERTS KNEE KICKER, CARPET TOOL 10-412-2 NICE! Y3
Roberts Knee Kicker Carpet Stretcher 10-412 Adjustable
Roberts Knee Kicker Carpet Stretcher 10-412 Adjustable Dial USA
