as was mentioned, the Honda 2000 has a vent cap that can be closed.
if i didn't have a pickup bed, i'd still have no problems carrying it in my vehicle or trailer.
i would put it in a plastic tub with a lid, like a Rubbermaid one.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC