Free: Contests & Raffles.
You have plenty of time to acquire a real set of antlers. Either in a garage sale or online. Maybe check with a local taxidermist too. Look for a set with better than average mass. If I had to go back and buy the set of sheds I found in the woods, knowing what they have done for me, I'd pay over $1,000 for them.
Not trying to thread jack but whats wrong with a rattle bag? I've seen them at cabelas. I've seen them used successfully on hunting programs.