Tiller Locks
The West Marine catalogue has two solutions for $19-$22, but if you're into minimal, try a simply lashing the tiller. On my previous C-27, I'd run a continuous line from the tiller. outside the stanchions up to and around the mast. There was enough friction in the system to hold the tiller in place, and I could steer from anywhere from the cockpit to the mast simply by pulling on the line. It took a little practice to know which direction to pull to turn port or starbord from the different locations, but it made single handing a lot simpler and safer.