I don't know how prevalent this is on airheads, but on my old beetle, it seems to happen about once every 2 years. And it just happened on my airhead and I had to wait about a week for the part.
Oil pressure sending unit. The plastic will crack or something and instant oil leaks. Sometimes bad enough that you are losing too much oil to continue your journey.
If you don't want to carry a spare one with you (which might get old and brittle by the time you need it, YMMV), go to the hardware store and buy a metric bolt. M12 x 1.5 is the type. Saw it off with a hacksaw to about 0.5" which is the depth of the oil pressure unit.
IMPORTANT!!! Make sure you de-burr, file, touch-up the cut you made so that there aren't any burrs. The reason is because usually the bolt you buy at the hardware store is going to be steel which will cut and mar the threads on aluminum engine block. Make sure the bolt will go almost all the way in by hand with minimal resistance.
And make sure you use the crush washer.
Also, on that same note, my stock tool kit did not come with anything that would fit the 24mm oil pressure switch. Might want to add a deep 24mm socket to the tool kit cause you're pretty talented if you can get it with a crescent wrench. (I couldn't.)