We'll probably eventually see 9mm 'guns' so small that they are also Zippo lighters!!

But I think that if you're trying to shoot anything 9mm or larger out of a gun that weighs less than a pound unloaded, your hand is in for some major sting and hurt if you shoot very many rounds.
It's basic physics--lighter guns and more powerful bullets equal more challenging (and usually more painful and inaccurate) shooting.
Even the little Rorbaugh R9 (ONLY $1195!) which is 15 ounces unloaded and 18 ounces loaded (7 rds) is only able to minimize 'hurt' just a bit, because of their unique spring and a few other features (no +P ammo, etc) and they strongly suggest you replace their special spring ($5) every 200 rounds. The Rohrbaugh HQ recommends you shoot it enough to get familiar with it, and be sure your carry ammo works in it, then stop firing and carry it.
So if
they can't make a small gun for that price that's comfortable enough to practice with say, shooting 50 rounds at a time, it's a tall order for
any manufacturer!
For a reasonable price, even though I've never been a fanboy for Taurus, their PT709 9mm model--(the Taurus 9mm Slim), and the 40 varient the PT740 (same size & weight) are two of the better guns in this segment, coming in at about 19 oz, and they conceal rather well. I couldn't believe my gunsmith when he spoke well of them for C&C and as shooters, but as usual, he was right.