Wow, they did a great job of making the strap invisible under the skin tight suit.I dont have a pattern for the cape itself, but I did do quite a bit of research on the costume when I made my Superman suit about 10 years ago. The most interesting thing I found out about the cape was how it attached to his body.
In photos, you can see that it seems to tuck into the blue neckline... At the end of one side there was a long strap attached right to the cornner of the cape which run down his chest, under his arm, around his back and then came out from under the other arm, over the chest and connected to the other top corner of the cape.
This put all the stress of the cape hanging on his body rather than right on the body suit since they didnt attach in any way at all. I found a great photo of a rack of capes hanging and you can clearly see how it was done. (although I'm not certain I can find a copy of the photo anymore, but I'll have a look around.)
It seems that more recently I've seen another photo of them putting his suit on and the strap was attached to each corner of the cape and connected in the back not unlike a bra strap. I also found the cape was wool, perhaps much like the new cape, except the new one is layered with latex...
Not sure that its much help, since I cant provide a pattern, but hopefully it will help.
Matt strikes again.