Past Parts will refurbish old brake cylinders with stainless sleeves. I did get a quote from them but it seemed fearfully expensive to me. In the end, I decided just to use some red brake grease to keep the corrosion at bay.
Edit - I've just looked up the quote and actually it was £60 + VAT + shipping which I guess isn't too bad in retrospect. Problem is that you can get brand new ones off eBay for nearer to £10 all in.
