It depends on what you mean by "on the market", and what you mean by "high volume". There are guys who could be acquired, but the ones who are proven to fit that profile are going to be expensive, and the Spurs have been -bent on keeping themselves in cap . I've been screaming about that for three seasons, and this is the reason why. One of the only ways the Spurs are going to get the guy you described is to find one who isn't currently getting the minutes, and so isn't getting as many 3PA/game. E'Twaun Moore with the Pelicans is one of those.
Still, the Spurs could have added a guy or two that would have been a lot better than this. A few years ago, I screamed for the Spurs to pick up an undrafted guy named Fred VanVleet - you may have heard of him. Max Strus was undrafted this year, same deal. (Strus got badly injured recently, so we may never know.) I also wanted them to snatch Darius Miller out of free agency this offseason, for the same reason - he got hurt too, so maybe I just have a knack for picking injury potential.
The Spurs could improve this team today if they would spin Forbes for whatever they could get, and put Walt Lemon on the roster in his place. If they got Lemon the shots Bryn is getting, I guarantee you he would have the 3P% to earn the minutes. He's taller than Bryn, he's a better defender than Bryn, and he knocks down the 3 ball. And unlike Bryn, he could actually make defender pay for running at him too hard, because he could actually get past them to the paint. Just let him play the 2 like Bryn, and the team improves. Forbes may put up some points, but his horrible defense makes people around him worse. And DDR is the one that really suffers from it the most.