The John Masen unit pictured by Dpmmn above is a good unit.  IMHO, it adds a bit too much length to the rifle, and I question adding a bayonet to the thin Mini barrel.

A shorter, handier size is employed by the Choate Machne and Tool FS:www.riflestock.com/catalog_page_detail.cfm?queries_index=index6&title_bar=Mini%2014%20Recoil%20Compensator%20Cage%20Blue&Manufacturer=&recordno=1&Product_CatalogID=343&ProductNumber=070712&ProductCode=54&NewProduct=0.  It mimics the A2 style  FS, and is also closed at the bottom to add a little compensator effect.  Just enough to do the job and no more.  Stainless and blues models are available from Bushmaster,  of all places.
The Eagle unit is also a quality product.  Some find the H+K style ring irritating.  I've seen some with the top 1/3 cut off to open it up.  YMMV.

It's possible some discontinued styles will re-appear after the Ban sunsets  Attaching a FS before then might be legally problematic.  I'd hold off and see what the options are.