There were 2 generations of Cobra's prior to the 1973 revamp with the shrouded ejector rod.
First generation Cobra's have a full length grip frame. Better stocks are very hard to find for them.
Second generation guns are the most common, and have the same grip frame as the post-1973 guns. There are many options for them. My suggestion is Secret Service stocks from Eagle Grips. They are great for double-action shooting but are still compact for concealment.
Nickel plate can be removed, but it will leave the parts slightly under-sized. You could have it stripped and re-nickeled, but it won't be stupid cheap any more.