You can get boomerangs from Prince. Just call Prince customer service and they will mail you one in a week.
But if you need one right away, an S hook will do the trick, but I have not tried the method, because I have a brake on my machine and I also have a set of boomerangs.
If you want to try the S Hook method, search YouTube.
Machines: Gamma 6004 2-point w/ Wise 2086 & Babolat Sensor Dual