I live alone and almost always cook just for myself. With most recipes, I can just cook a smaller amount than given in the recipe, and I have optimized most of my cooking gear for small quantities. But I have a problem with some dishes which are both too rich to eat more than one, maximum two portions in a day, and too perishable to store for longer. Some of those, like the egg foams (zabaglione, hollandaise) and some sweet dishes involving melted chocolate, require a bain marie.   I don't have the storage space for single-purpose gear. When I need bain marie, I use a regular pot and a Pyrex bowl whose upper diameter is somewhat bigger than the pot's. My smallest pot is 16 cm, and a bowl which fits on it is too big for one or two yolks. When I try beating them, they smear themselves on the walls and cook there before they've flowed to the bottom. Also, the heating is somewhat quick, because the whole mass is only 1 cm thick or less. Making 40 g ganache is no easier.   I prefer beating such small amounts in a tea cup or mug or in a 6 cm bowl, inserting a single beater into the mixer. But I cannot do it when I need a bain marie, because I have no pot where they'd stay on top. And even if I could find a small replacement for the pot (like a steel mug or a djezwe), it won't heat on my induction hob - even if the "pot" was ferromagnetic, the hob  has a built-in protection and only switches on if it detects a cooking vessel at least 12 cm wide.   Do you have any ideas for an easily built bain marie setup which is small, uses common utensils (not necessary kitchen ones, but preferably something I already have), and quickly dismantled when not in use? Maybe there is some way to suspend the tea cup into the big pot and hold it firm despite the mixer's force?  
OK, this is an ancient question, but the biggest issue is the induction aspect. No one appears to have suggested using an induction adaptor to allow the use of a very small pan, like a Turkish coffee pot, for the bottom part.  That would get you down to about 10cm diameter, with a small Pyrex bowl or wide cup (cappuccino cup) on top. Convection from the induction adaptor heating the upper bowl shouldn't be too much of a problem, though the adaptor plate would get rather hot.  Bialetti's at least is clearly designed for pots smaller than the induction ring. This adaptor plate would seem like a useful tool to have, but if you have a non-non-stick induction-compatible shallow pan that would also work, with the  cezve inside it.  You may, for example, have a cast iron frying pan you'd use for dry-frying flatbreads (I do, anyway), and that use would be similar in the sense of heating it dry.  Alternatively I'd make a frame from stiff wire, to allow suspending a small bowl over a larger pan.  Personally I'd use stainless steel  bicycle spoke, as I have plenty.  They don't touch the food itself after all. Coat hanger wire might also be stiff enough.  Either could be formed into the right shape with bending, using twisted joints (requiring two large pairs of pliers).  Aluminium foil could be used to avoid steaming your hand. 