I had similar on my Boston Whaler Harpoon 4.6. They are not particularly trustworthy, though when I took the Harpoon out for capsize drills, the spring stop worked. Nevertheless, I still tied a tether to the headstock, just in case. You could probably use any old piece of thin SS tang stock to make one.
My 192 has a hole drilled in the top pintle, and a hairpin cotter pin goes through the hole to keep the rudder in the gudgeons. If your isn't set up like that, you might consider doing that. Not that drilling the pintle will be easy, but eventually...
For my Force 5, I replaced the notoriously weak spring rod with a 3/8" 316SS hex bolt, and drilled a hole for hairpin cotter pin. Lemme tell you how much of a PITA that is using a hand drill... Just bought an 8" bench top drill press from Harbor Freight. Next time I need to do something like that, it should be much easier with the press, running on slow speed of course.
Just for fun, here are pics of my Harpoon spring after I bent it all to shit while simultaneously wrecking the trailing bottom corner of my rudder (don't ask.
):
And here is is after I went to town with a couple pairs of pliers:
And finally after I beat on it with a flat hammer against my vise anvil, then put a bit of bend to the angle:
It worked fine after all that. Let's not talk about the fiberglass repairs I hadda do to the rudder...