Trailer wheel bearings
 

I have an extra set, seal and cotter pin in a Tupperware bin I take along incase. Had one blow up once and didn't have any parts. Ran all over to find stuff.
My friend got a spare set and used his vacuum sealer on them. I would be afraid of greasing up sealer and wife finding out. But he said it worked. Sealed up a set for his dad and uncle too.

I just carry a spare hub already greased and ready to go. I like the idea of vacuum bagging it. My trip to the ramp is only about 5 miles round trip, so not an issue, When we were going to the keys, trailer problems where a major concern.