Based on a need for this little doo-dad, Gordon and I both came up with low budget solutions. If you are missing your trip reset knob, here are two options for replacements... Good luck.
Maybe it's been used on this site before, but I just tried the electrical cap (thing used to screw two wires together) to reset my trip meter. I cut the depth down with a dremel, and it fit right on there and reset it WAY quicker than when I once tried the needle nose on there.
I took it back off and stored it under the seat, but it seemed like it would have stayed on there if I had worked it in a bit more.
Now, once I get this thing chromed, I'll be all set....
I was inspired by this thread to finally attempt to do something about the missing trip reset knob on my 550.
I've had a repair kit to replace a table lamp switch in the top drawer of my dresser for several years. I never really used the lamp much in the first place so never got around to fixing the switch after it broke. It's the perfect size, and even looks half-way correct as a replacement trip knob. I reamed out the hole with varying size screwdrivers until it was a snug push fit on the reset shaft, then put a dab of silicone gasket sealer in to keep it from vibrating off. It works great, so far, and I don't see any reason why it won't stay put. It doesn't take much torque to turn the trip odometer, so it shouldn't work it's way off when used. We'll see.
