Prime Winner:
I just secured a set of Meprolight Night Sights for the Sigma from opticsplanets. $77 (free shipping).
Meprolight Night Sights for Smith Wesson Pistols, Revolvers and Shotguns FREE S&H ML11735, ML11755, ML11760, ML11765, ML11766, ML12740, ML22770, ML22771. Meprolight Tritium & Fiber Optic Night Sights.
Warning:
Sights are backordered. They don't post it anywhere and do not warn you when placing the order. Then, after ordering, they send you an email apologizing for it being back ordered.
argon