I don't know. I started to go down that path but all the CDN's that suggested some aspect of try before buying were in places outside of the US and had non US payment processors so I moved on to other projects. I doubt that there are many. I suspect Cloudflare only do it as a result of dual-use and that dual-use may be backed by tax dollars as there is no way a publicly traded company would give away massive network resources at a loss but that is my own conspiracy theory. i.e. an extension to Googles birds of a feather project. Capture most web traffic, most DNS traffic and learn who talks to who and why to form a risk map.