Cougfan2,
Like the PPK, the 232 front sight is part of the slide.
SiG offers night sights as a factory option but will not insert the tritium in the standard front sight. (Unless they have recently changed this policy, though I doubt it).
Those of us with standard sights are stuck with a custom install which, as mentioned, would mean either having someone drill a hole in the front sight and glue a tritium vial in there or milling off the original sight and milling in a dovetail that will accept, say a sig#6 or #8 or whatever style dove-tailed front sight.
SiG offers the rear night sight, which will fit in the standard rear dovetail.
Mayhap, Trijicon & Meprolight offer replacement rears as well.
May be a little more costly in the long-run, but you can figure out the exact sight setup you want (within reason, a globe front and rear Bomar might be a little too big) and have it custom installed by a good smith (the milled areas will at the very least need cold-blue on up to a complete slide refinish) and be all set.
Easy