Every once in a while a hood shows up on Ebay. That is where I got mine. There is also someone on there offering a 3D brush guard and sleeper, although a little pricey in my opinion. It will take a bit more than lengthening the AMT hood to make an RS700L hood as the fenders are a little different and considered low mount fenders, but it can be done. I hope to convert the AMT hood to a short RL600 hood one day.
Like was said before, call Dave at A.I.T.M. direct and if he can help you he will, he is great to deal with.