Actually, I've tried DSE, Tandy, and Supercheap today, and none of them have the single can units.
Who's to say I haven't made one?
The commercial units usually use only one Peltier device,
but there's more to it than sticking it to a can and hoping the drink gets cold.
You have to have a surface that mates with the can, the can has to be insulated,
and the reverse side of the Peltier requires heatsinking.
It's easier and cheaper to buy one than to make one.
They are on eBay in the plenty, but I was hoping to locate one sooner
than the delivery would take.
As long as your insulation is good using any more than one Peltier is just wasting power.
They will cool quicker, but no colder.