It would probably be easier for you to make a new mirror for it than actually find one.
Mirror making isn't a hard job to do although it does take time and some effort. There are a fair number of mirrormaking articles on the web and I have several of them at http://bobmay.astronomy.net amongst the stuff there. You will need to take a little more care getting the ROC to what you want but it is quite doable for the first timeer. If you have somebody in your area who has made a mirror before, he can usually be persuaded to assist in the technical details that will make life easier.