We ended up getting a stainless steel one, cheaper in the long run and no rust. We got ours from M&S a couple of years ago but a google search should find you one.
I took the shelves off the pole and stuck then straight onto the tiles with extra strong adhesive. Lasted for ages, in fact when we had the shower renewed, the builders had to use a crowbar to get the shelves of the tiles...
We got ours from Bathstore & it hasn't rusted in 7 years. It cost £90 but I think they do smaller ones which are cheaper. Ours has two shelves and two pump dispensers for shampoo. I think they do just one shelf on its own