An even better option is to get a "new" key cut from the digital code - rather than copying the worn-out original key. I bought a genuine key blank ('89, lighted head) from our host and had it done by this guy:
Keys for Classics, specialists in code-cut keys for classic cars and motorcycles
He (Stuart) interprets the code from a couple of clear, digital pics of your original key; you do not have to send your original key anywhere. He has a zillion different blanks, including early Porsche ones.
He's down here in Oz, but has been doing this for 10 years or more and told me that the US is his biggest market. (I'm a journalist, so I always ask lots of questions).
With my "new" key and a few drops of light oil in the barrel (I used Parma slot-car oil), it's almost like new. I've since had a new spare key cut for my '72 MV Agusta bike, too.
I have no association with Stuart other than as a customer, but I recommend him most highly.