USA
Some are made in Exeter, NH, but some are still made in Germany.
50-550 usd
You will have to call SIG. They also offer a letter for a resonable price.
No. You can get a Sig P229 that will fire .357 Sig, but that is not the same as .357 magnum.
The answer is yes....and no.
By performing a barrel swap to the 357 sig barrel the gun is capable of shooting the 357 sig round. However, the 357 sig has a much higher barrel pressure (5000-10000 more psi).
While the gun can shoot the 357 sig round simply by changing the barrel, this will cause more wear than is normal and can possible damage the slide.
The safe bet is to buy a slide and barrel meant for the 357 sig round.