Gun shop, gun show
triplek.com
The Kimel firearms company is out of business, so your best bet is online. Either gunbroker.com or try Numrich Arms.
Try gun shops, pawn shops, want ads, for sale ads, garage sales, estate sales, gun shows, on line auctions
Try e-gunparts.com
Which model? If it is the t9 or t8 pistol then you have to buy an adapter for a 20 oz tank.
Contact the maker, want ads, gun shows, gun shops, internet auctions.
The best you can afford from any reputable maker.
In the US, you need to locate a dealer in your home state that has a special license ( commonly called a Class III) to sell suppressors. You will need to apply to the BATFE for transfer of the suppressor to you, and pay a $200 tax on the transfer.
You might try a search on Commemorative Arms Co. Supposedly they purchased a supply of repair parts for the Nomad, Challenger, and Medalist
Yes.
Sig
I do not think you can. Please rearch the Indian Arms Rules of 1962. While India DOES have a licensing process for some firearms, the IMPORTATION of most firearms is sharply curtailed- and THAT pistol is not made in India. Sorry.