OK, starting from the last one, the mr55 link, that one is not good for stones, the insert doesn't come out, meaning you have to lift the whole thing up to empty it. This also means there is no water around the element, and all those venting holes on the side are allowing hot air to come out into the room - probably be hotter than a roaster to use!!!! It's more like what I've seen called a bain marie out here, the trays are twice as deep as the chafers (Bain marie ~6", chafer ~3")
The Buffet Burner - it's heating the air between the burner and the chafer, so some of that is bound to come out into the treatment room, though it's a low wateforum.xxxe. I didn't spot any price on there, so it might be a way for someone to go from a normal chafer that using burning fuel to convert to electricity cheaply or expensively (I do know of someone that uses a chafer with the usual burning fuel pots underneath - she only does a hot stone treatment every month or so, and she already had a chafer, so it was all very easy and cheap. She says it works well. something like this would be good if she had more treatment and wanted to stop using fuel)
The ChaferDepot one looks good, that's the same as the Sunnex one I posted a link to, water bath under insert, removeable insert (I do know someone using the Sunnex one and they have no complaints) The price is scary - that's a lot more than they are in Australia! One of the resorts out here is using a brand called Salgo, and they are about a third less than the Sunnex.
All of these being commercial catering equipment, you may be able to find them on eBay, or second hand, maybe not garage sales, like someone on here got a roaster for free for their stones