Try at forestry supply stores. The guys that sell pulaskis, fire pumps, etc. They have the entire setup for portable kitchens.
The ones I've seen were a separate stove and bottle, but the stove and pedestal were sized that the stove would stack on the bottle.
We used such a rig on a large canoe expedition, and used a pot that would fit the bottle and stove. We could boil 5 gallons of water in about 20 minutes.
Yes, you will need a regulator.
You could make one of these yourself. You'd need a regulator, a short hose, a stove, then some form of adapter fitting. That you might have to make, or hire made.
Short brackets bolted to the upper flange of the bottle would support the stove. You need room to turn off the stove valve. It's also a good idea to have at least a reflective layer between the stove and the bottle so that the stove doesn't warm up the bottle too much.
Stability is a concern, but is certainly no worse that the first stove pictured. You definitely want an auto-shutoff if tilted.
I think that the height of your proposed unit is actually inconvenient. It's too tall to use sitting down, and not tall enough to use standing up. If you are using while car camping, you almost always have picnic tables. A stove that sat on the table, and connected by a short hose to the propane bottle below would be far easier to use.
The downside is that you need to detach the hose from the bottle each time. This requires a wrench. We had enough experience losing the wrench that we tied it with a 2 foot rope to the ring on the bottle. The wrench applied to the bottle made a good supper bell too.