Harbor Freight has a new item currently on sale, a telescoping
aluminum flag pole, item 92901.  It extends to 16 feet, and can be
locked at any arbitrary shorter length down to the 62 inch collapsed
length.  The bottom section is 2 inches diameter and the fourth, top
section is 1.5 inches diameter, so it's easily self-supporting if you
have a way to secure the base.  It's about 6 pounds.  There's a top
ball that screws in, so there's a very easy place to add a little
plate for a place to attach guys.  I haven't had mine long enough to
try it, but I expect it will make a fine 20meter-and-above 1/4 wave
vertical for portable use.  With a bit of capacitive hat and a loading
coil, it may even work well on 40m.  If you get one, be sure that all
the sections lock properly--mine may get exchanged because one of the
sections doesn't seem to want to lock.

Cheers,
Tom