I purchased mine at a local company that carries truck accessories and snow plows. A friend told me the price went up a little this year and they are getting closer to the $300 mark when the rack and brackets are purchased. I didn't go with the safety rack because I like as much visibility as possible for snow removal. This rack still offers a lot of protection, visibility, and is a great place to mount lights and strobes without them being in harms way. Since I haven't had a problem blowing out back windows with wood (I have broken a rear power sliding window on my old truck, but that's a story for another thread!) the main reason I purchased one was for mounting lights in a location where I wasn't constantly breaking them.
If you are good at fabrication and working with metal you could always build one. A lot of guys on this site have built very nice, practical, well built racks that you could "borrow" ideas from. I looked into doing that, but after buying the steel, not having the "perfect" tools to complete the task, getting it powder coated, and drilling holes in my new truck, the time it would take, etc. I was better off buying one. I paid about $250 with the brackets and did not have to drill a single hole in the truck. When I remove it you can't even tell it was on there. I guess it depends on your skill level and how nice your truck is.
They do also make provisions for tonneau covers and tool boxes. They simply use different brackets. My advice would be to find a back rack dealer that has sold several and get the details from them, but I do know it can be done.