Dacor in the late 1970s made a BC called the Nautilus. I have two (one right now on loan, the other not quite completely outfitted), and have dived them. The nice thing about them is that the Nautilus is designed to be put on in the water. There may still be a few around dive shops. The Nautilus uses a different BC concept, in that it is a hard shell, and is not "inflated" but water displaces air like in a submarine. The full name was the Dacor Nautilus CVS (Constant Volume System). I'll show you a few photos of it:
Here the Dacor Nautilus is floating with about 16 pounds of weight in it, an 80 cf AL tank attached and using an older style double hose regulator (Sportsways Hydro Twin). Obviously, I'm not in it.
Here's what it looks like with yours truly wearing it.
Here is what the unit looks like with a USD 52 cf steel tank mounted on it and a Dacor Pacer regulator. Note that there is another regulator on the inflator hose which keeps the unit at constant pressure with the surrounding water when the diver descends with the bottom valve closed.
And here is the unit from below, showing the control valve and the quick release weight chute.
The weights are mounted inside:
Why am I showing you this? Because it is designed, like I said above, to be donned in the water. Open the bottom control valve, then open either the top valve or the inflator hose and flood the unit until it stands vertical in the water. swim over, get into the shoulder straps, cinch up the waist strap and it is on (get the regulators positioned though). It is an option, but you'll have to scrounge around to find one.
SeaRat