Why is it that outboard manufacturers create a shift lever that is pretty much inaccessible on a small engine, and then don't offer an accessory extension handle for it???
I have a new Honda 5hp 4-stroke engine with that issue. The shift lever is completely irregular in shape, making it difficult to machine something that would fit, as I've managed to do in the past for other engines. There is even a hole in the shift lever to attach something, but nothing exists to attach, not from Honda nor any aftermarketer. What were they thinking? (I'm well aware that aftermarketers make extensions for the throttle handles. I have one. No extensions could be found for the shift lever.)
I solved this using a length of Schedule 80 PVC electrical conduit. The first length was the piece that would go over the shift lever, and the other two lengths were PVC-glued onto the first piece once the assembly was dry-fitted to check for clearance so as to not rub against the engine housing.
The key to getting the first piece onto the shift lever is a heat gun. Careful heating, always moving the heat gun, softens the PVC. You want it just hot enough to be pliable, but not so hot that it buckles when you force it over the shift lever. When heated well, the piece slides over the the shift lever with a bit of force and conforms to it's irregular shape as it cools. The other pieces can be fitted and glued after that, taking care to be neat with the PVC glue on the conduit pieces, and avoid getting it on the engine housing.