Like
this one?
In stock at HRO.
I expect signals to be weaker than a vertical whip.
And, given the whip can be made with thin wire or
brazing rod and painted to make it unobtrusive,
I doubt the loop would be more stealth. Besides,
there is a null in the loop pattern, so it isn't
omnidirectional.
My "stealth" antenna for transmitter hunts that I
hide in plain sight is a yellow wasp trap, with the
transmitter inside. The 2m antenna is an 18" black
wire that the trap hangs from, with 2 black wire
radials draping out the bottom. Everybody ignores
it, until their antenna points straight at it hanging
in a tree.
Do make sure that you seal the holes in the trap first,
however.