Simply apply the lesson learned and move sooner/quicker ?
$300 for a tiller?? Holy Cow, that's steep! T'were it me, I'd make one out of *something*, just ta pi$$ off the drmarine guy, and THAT one would have a security cable/tie.
Ya learn from mistakes; not success'. Good that it's a dink, a waist deep warm lake and inexpensive....no really!.... parts. Better there than out to sea on a $150K boat and have yer first "whoopsie" happen!
Best...and keep sailin',