What helmet do you have?
You could make your own pattern by taking pieces of thin paper inside the helmet and tracing the individual shapes. Put them all back together and see what you come out with. That way you might only go through 19 yards of fabric.
Pattern might not have been a bad idea. I did one for my helmet using some black vinyl and just kinda made it on the fly. Did it in 4 pieces, with some seams that will be hidden by the interior padding/MS kit. I cut out pieces for the back/sides, the top section and forehead, and the mandibles. All in all it was fairly easy, and the only piece I had to redo was the top section, all attached with hot glue.
Funny this thread should come up....I'm actually in the middle of doing this myself. I've selected a "marine vinyl" that looks and feels like real leather. I am using this as a liner in conjunction with my MS interior among other greeblies and such. I basically just hate the look of black/gray painted fiberglass that are more commonplace.
It's not going to cover every square inch,but large portions so we'll see how it goes....doesn't appear to bad if you know how the material will fold,crease,bend. I bought 1/2 a yard and seems to be plenty. I'll make templates out of paper first to at least get a feel for how much to start cutting. I'm sure it will be a cut as you go deal until a perfect fit it achieved....then glue. I'll be using Elmers white glue since it dries fast,has water clean-up and dries clear.
I'll be sure and post pics in my 'MS interior thread' when it's completed the the next few weeks.