Canonical Tru(e) Blood Information
First of all, as far as I know nothing even remotely similar to the current "Followers of Lilith" storyline occurs in any of the novels, and True Blood doesn't appear as a serious plot element anywhere. It's mostly just an excuse to explain why vampires decided to reveal themselves when they did.
On the TV show, the loss of the Tru Blood factories has sent vampires into somewhat of a frenzy. Bill explicitly mentions that there are only six in the entire world. And Tara considers hoarding it when the factories start to go offline. All of this strongly suggests there is no alternative source of Tru Blood or anything similar to it; if anywhere would know about it, it's a vampire bar.
Thus, there's no canonical indication in either case that anything synethetic, other than Tru(e) Blood, works as vampire sustenance.
We can, however, use what we know about it's development process to speculate about its rarity.
From a research standpoint, the substance was discovered by Japanese scientists, but otherwise we have no idea what it contains. On the TV program, there were references to the efforts that vampires had put into developing synthetic blood (I think it was mentioned that Pasteur himself worked on it), which means there would be hundreds of years of research to build on. The fact that it was only recently that a viable synthetic blood became available implies that there are very specific and unique requirements for the substance to work.
It's also very likely that the substance, even once it was discovered, is very difficult to make, possibly requiring hard-to-acquire chemicals, or hard-to-manufacture equipment. That would also explain why there's only a small number of factories around the world, and why they cannot simply replace them.
Given all of that, I think it's unlikely that a cheap alternative to Tru Blood is going to pop up any time soon. I wouldn't be surprised if people continued to work on it, much like they continue to look for cheaper or more effective pharmaceuticals, but if one was ready for production at this point it certainly would have made itself known.