Use the Force! (Seriously, yak fishing =/= Star Wars? There is no "Hobie Wan Kenobie" poster here?!?
I can't think of a way that wouldn't easily fall over... I thought of PCV piping with a hole cut near the bottom on one side that the handle could slip in with a 'mousehole' cut out on the other side so that it could lean backwards and possibly be out of the way and work like a rudder but I'm not sure if that material is easy to cut like that... and would be tippy left or right if the holes weren't just so. Maybe two holes, one slightly higher than the other and fit the steering handle through both if the holes had a flat bottom (not just round holes)?
Alternatively maybe on the other side where I believe there's a dial (might have the PA's mixed up) a thin PVC pipe with a slot/slit cut across the bottom to fit over the line on the dial? Would vicegrips squeezed on the bottom hold it on? Both might need leashes...
Top either with a bad a$$ skull shifter
Just trying to brainstorm as I can see fine tuning the steering while standing could be handy... I don't even have a yak, let alone have any experience tweaking things... My $0.02 comes with change back