I have a 2007 Rainbow in good shape that I'll let go for a great price - $60 plus shipping. It's nearly the original model - velcro closure for the fly - but it does have the length adjuster for the pole.
I've always used it with a ground cloth and haven't used it much at all for several years since I got another single rainbow with a zipper closure (I'm 60 and it's getting hard to bend over...)
I love these things. I'm on the Olympic Peninsula and they've kept me and my down bags dry many times. They have never let me down.