This company advertising on Milweb are making new 17pdr Muzzle Brakes - no idea how much, but thought it might be of interest to some here.
http://www.milweb.net/webvert/a1897
David Moreno
+34 639 421 809
dmbmadr -at-Hotmail -dot- com
Would appear they will cast most things with a pattern.
No idea quality or cost as have not bought from them.
Tim