One small company down in deepest darkest Montana took it upon itself a few years back to develop a few worthwhile accessories for a military surplus rifle/carbine that most people, even shooters, had never heard of - the Swiss K31. Design and developent of of a genuinely functioning muzzle brake for such a minority interest firearm was never going to be cheap, nor was it ever going to make the manufacturers millions of dollars.
Hence what might be seen in some quarters as expensive bits of tin with holes in that simply clamps, or threads onto a strange-looking rifle/carbine.
Nobody else has EVER made a muzzle brake for a Swiss straight-pull firearm, nor I doubt, ever will. Nobody else I know of makes the current range of accessories for them, either, except Swiss Products of Kallispel Montana.
The price from Tradex, sad to say, is their price, and this reflects the pricing disparity between Canada and US, where it sells for $75.
As smellie notes, for sure you'll be as popular on the gun-line as a fart in an elevator - effective they sure are, but unfriendly in the extreme.
Get a PAST reducer.
tac