Choices...
Buy the $34.00 OEM
guaranteed to eventually leak again no matter what you do neutral switch or install the better designed $21.00 Italian-made repop switch from Motobins.
Shipped via Royal Air Mail at the low cost Packet Rate (lower than UPS rates within the USof A), my new switch arrived in four days. Lucky there, I was.

The rear motor mount bolt, plus the hefty aluminum spacer tube, must come out. Block up the engine
before removing these parts. The engine must be secure and by taking the load off the bolt, it can be extracted easier.
Disconnect the two wires from your metered leak. Clean the connectors and be gentle with the vintage wiring. Remove the neutral switch and see how far you can throw it. A very cathartic action.
Use a new crush washer. Don't cheap out here or you may end up doing this whole procedure again. Argh! I believe the shop manual -
or someone who has never actually done this job- says to use a box-end wrench to snug up the new switch. Once you get to that install point, you'll see that's impossible. OE and just snug it up.
You may be advised to put the honkin' big aluminum tube in the freezer so it will "shrink" and be easier to install. Try it. It might work for you. I went the easier route and ground a slight 45 degree angle on each end. Less than 1/8" width is plenty to assist the tube back between the frame rails.
One of those bent-tip, angled pry bars from Harbor-Freight and a plastic mallet eventually encouraged the refit.
This is one of those jobs that you want to do only once. Afterwards, reward yourself with the adult beverage
s of choice.