They came with a Limbsaver Stabilizer Enhancer I had purchased. I was'nt sure which accessory they had come with but now I'm quite sure. Perhaps a call to Sims? It did'nt have that collar on it though.
If you cant find them commercially avalible you could try contacting a local machine shop and have them made,but this might be expensive.
check with coolhandluke on AT he was look for the same thing about 8 months ago for his Vibekiller for a Hoyt Elite bows. I know he eather makes them or can tell you where to get them. Tell him shovelhead80 sent you.