You could either rent a Prince Charlie and accessories... or you could try and pick up an ex-rental tailcoat and get a local tailor to turn it into a prince charlie for you. There are some threads here on how to do that. You'd still need to order the metal buttons.

Piper hose are a good deal. Scottish Lion has them at $22. Get dark ones for formal wear.

If he just has regular shoes, I wouldn't bother lacing them around the ankle like ghillie brogues. Just wear them like regular shoes.

While you're picking up the tailcoat, see if you can get a backless three-button vest from the same place.

That's about the best I can suggest given the budget in question.