Any ideas How I can do these or if there is some sort of mould out there? These need to be white and sticking out of mini cupcakes...

You could make them out of royal icing or fondant.

I saw cutters somewhere with a mini Magen David. I'll try to remember where!. They might have been too big, though, for a mini cuppie.

I went to a local baking supply store and found a sheet of stars of david that you make with candies, perfect size for little cups!! Now lets hope they all stay upright wile I transport them to my client :S

I'm sure there is a little star chocolate mold that you could use.

For next time, FMM makes a "Christmas Cutter Set" that is two pink plastic strips of small designs kinda like Tappits. There is a small Star of David in that set - it is about 1" across.