Andt
the Festool part number is 493566 which any dealer can order. From memory its about £10. You will still need the brass bush 711TP from Leigh.
The 1400 is excellent on the jig but the whole Leigh experience is transformed by the addition of the new vacuum router support. No dust or shavings at all and no router tilting. It really does do exactly as it says on the tin.