My resident expert on fabricky stuff says a "Micropen" should work, but you'd probably have to go to a hobby shop (like Michaels) or fabric shop (she goes to JoAnns a lot) to find them.

Lin says she's used them on other kinds of cloth and they should work ok on silk, but of course you'll want to try one out before charging off and leave a trail of blots.

WallyWorld should have "fabric markers," sort of a glorified felt-tip pen, and they come with permanent ink or with an ink that will wash out, so you have to watch which kind you're getting; but I suspect they'd bleed into silk.

John