Two options I'm aware of:
Letech ladder replacement:
Der Zugang zum Dach wird durch die LeTech Heckleiter ermöglicht, die zudem über eine praktische 20-Liter Blechkanister-Halterung und eine Skiaufnahme verfügt. Die LeTech Heckleiter wird inkl.
lennartz-technik.de
NashFabCo:
2 Week lead time before ship out! NashFab single jerry can carrier: -inside dimensions 19" x 14 1/4" x 7 1/4"-made of 16ga steel-weight of 13lbs-comes powder coated a matte black finish-comes with all necessary stainless steel carriage bolts and strap-single strap that has several adjustment...
www.nashfabco.com
-paired with this:
1 Week lead time before ship out! ROTOPAX MOUNT AND GAS CAN NOT INCLUDED... product features: +Constructed of 14Ga steel+Powder coated a matte black+ light weight, weighs 3 lbs+this mounting plate hinges open allowing access to still climb your ladder+able to mount several different...
www.nashfabco.com
The above combo creates a swing out fuel can ladder mount. It requires pairing the right mount attachments to the ladder. I haven't gotten around to asking NashFabCo which mounts would work with the round tubing of the Grenadier's ladder.