I looked for it on the net a while ago and I could not find it via legal means. I asked Boss Monster on Facebook if they would make it available again and they said that they might. With the release of Boss Monster 2 this month, I am sure that a lot is about to change for this game.
But I do not know of anyway to get a hold of the strategy guide right now.
Feel free to discuss or ask about strategies on this forum though. I have not played this game in a while, nor do I really plan on doing so soon, but I know that at least I am willing to discuss strategies.