I'm sure there is a spray paint called "plasticote" or something similar. Presumably that might be just the ticket. You could spray it onto a saucer, and dip a brush in.
It might be worth asking one of the companies that sell replacement doors for kitchen units. The people we bought our new doors from had all sorts of odds and ends.
I am hoping someone knows the answer to this one. I have some slight damage to a kitchen unit from moving a fridge freezer in/out. Is there such a thing as tiny pots of a cream coloured plastic type paint for touching it up?