Geoff Mendleson offered some good advice.
The dipole he suggested can be made using one 19-inch whip as the upper
half of a vertical dipole and a 19-inch metal tube as the lower half of
the dipole. The tube is also used as a sleeve over the coax which feeds
the dipole at its center.

This antenna is often called a coaxial or sleeve antenna. It is also
often disguised to appear as something else such as a flagpole, etc.
This antenna has 0 dBd gain and is omnidirectional in the horizontal
plane. It works well in almost any line of sight direction and so is
useful with portable and mobile stations. It is as good as a ground
plane antenna without projections to cause injuries.

Best regards, Richard Harrison, KB5WZI