I have a New-In-Box Surefire Mini that I recently ordered from a dealer on Gunbroker. Surefire suppressors are known for their low POI shift and rock-solid QD mechanism. The mini is ideal for an SBR, adding only 3.3" to the OAL.
This model can be had for only a fraction of the cost of one of the newer "SOCOM" series suppressors.

I am asking $500 and the suppressor is currently on a Form 3 at my dealers location in Warminster. Does not include a mount/adapter, but I have found several locations that sell them for an affordable price.

Pictures below are stock photos, but represent what you will be receiving.