James asked:
Aren't all hand-held HAM radios line-of-sight only?

No. There are a few HF hand-held radios, and HF can bounce.
Hams make homebrew, kits, etc HF radios that are tiny.

An effective antenna may be larger than you prefer though.
Likewise, some use a bigger antenna for uhf/vhf in emergency
situations.

Google on ARS Adventure ham
Google on "flight of the bumble bees" ham