I dont use one but I have been looking for one to use for something else, this is the best deal I have found http://www.motoin.de/Winter/Protectors/Dainese-Active-Shield-Evo-back-protector::27298.html
I haven't used the spine protector, but I have used the jacket, and it's ridiculously comfortable. I remember a friend telling me he removed the shoulder pads because it disrupted his throwing motion. Both are certified level 2.