If you need a mouse and keyboard, you are a bit stuck. The mice are easy top find, but only in the platinum plus color. The keyboards are harder to find; they usually only are found with a full 128k. The keyboard cable is important as well. It is not your standard phone cable. If you attempt to use a phone cable w/ a 128k keyboard, you could bust the board.

I believe one of Larry Pina's books has a section about converting phone cables for a 128k keyboard.