I have a few rush jobs at the moment, one of which is 60 cloth-covered buttons for Jane's Wardrobe. These are for a justaucorps - 1680s - and there are 60 to complete. Of course, being the odd person that I am, I find it very relaxing making buttons, even plain covered ones... These have a card base, which is actually historical - its not something that you find in a dig of course, but there are buttons where, when the mould can be seen, is cardboard. I suspect it is less likely on the very fancy passementerie buttons, (though of course, many of these are so well made that the mould cannot be seen) but is very suitable for plain buttons.
There is also the added benefit that there is no problem finding the correct moulds, no matter what size is needed!