Starline did indeed make a special run on special order of .41 SPL headstamped brass. I just bought some (250rds) a month ago. You can find it on Gunbroker. It is still considered a wildcat though , as no factory ammo exists because the round has no SAAMI* specs or approval.
As I found out the hard way , many ranges have a "No Magnum - Specials Only" policy. You cannot use ANY ammo that says MAG or MAGNUM. Don't matter if it's a squib load! Yet ya can shoot .30 Carbine , .454 Casull , or any other round that does not say MAGNUM on the headstamp. Ya can even load your .44 Specials to levels that would make Elmer Keith wince , but NO MAGNUMS!
I tried using my Horton/S&W 657 Classic Hunter in pistol matches a few years back. I made some mild loads , a 175gr cast SWC over ?.??grs of W-231 for about 800fps. Was told that since the rounds were headstamped MAGNUM , I could not use them! I then demonstrated the diff between one of my reduced loads and a full power .41 Mag load , 220gr SWC over 16.5grs Blue Dot.
Was promptly asked , er , TOLD to leave!
* Sporting Arms Ammunition Manufacturers Institute.