If you have any interest in a used one, I am going to be parting out a '69 912 when I get around to it, and I think the front glass is good. Should be the same. I don't think they changed them from 69 - 89. I could be wrong, but it should be easy to check.
Janet and I both had to get new windshields in the last two months. My insurance company (GEICO) recommended Safelite. They were very reasonable and did the work at our house. I asked the guy about a 996 windshield and he said about $250. You can get bids over the phone, and they are negotiable if you tell them you have some other bids.