You need the best pattern possible. NOS is the way to go.
Then just scan the part to capture the 3D geometry. Once you have the file scale it up, make the pattern and away you go!!!!!
There is an app for $3 that turns your phone into a hand held scanner and the data is good enough to use (we have done it)
Basic but ok. As you would expect for $3... The $3 one was the flash one. $0.99 will get you a basic app.
To do the job properly use professionals.
At the bottom end of the scale you can buy a 3D printer for £700 from a local electronics shop (Maplins) here in the UK. On ebay basic ones start at about £1000. They are no very good (but getting better at the time)
To do anything serious use professionals. You don't have to be buy your own, there is a Whole Industry out there waiting to help you. (and it doesn't have to be that expensive)