I made this from a thrift store blazer, rather than buying fabric new. It cost about $9 (in expensive San Francisco) and I'll get another 2 hats from it, easily. If you have fallen in love with yardage, you'll need about a third of a yard -- but take the pattern to the store and lay it out there to be sure.
For the brim, I use a piece of flexible clear plastic of the kind blister packages are made from. Many packages have large flat areas from which the plastic can be reclaimed, although a lot are just too closely molded to the product. I have a stash of flat plastic for brims. Yay reuse!
The only other material needed is a yard or so of quilt binding or wide bias tape for the inner hat band. Tools required are sewing machine (although you could do this by hand as well), pins, and scissors.
Update: pix of one made from paper! http://www.flickr.com/photos/29317731@N08/sets/72157617448800455/
Step 1: Pattern
I have not worked out a good way to get a paper pattern into a computer. If anyone has a good idea I'd love to hear it. Anyway I traced these in Photoshop... I didn't take the estimated 4 hours I thought it would take to add the seam allowance, so each of these shows only the stitching line. When you print them out, you'll want to cut a quarter inch out from the line; it may be easiest to draw the cutting line on first.
Also: the sizing is probably not correct. I marked a red line with a number of inches on each file, so you may need to make some xerox adjustments to get that marking to the right length.
Thanks for your patience everyone! Please post pictures of yours!
Step 2: Cut out pieces
1 x crown
1 x side
2 x flap
1 x strap
2 x brim, with seam allowance
1 x crown
1 x side
1 x brim, without seam allowance
Make notches as marked so you'll know where to match the pieces up.
Step 3: Construct crown
When you have both pieces together, press and/or topstitch the wool piece (I never bother with this for the lining). Then put the lining inside, wrong sides together, and baste around the bottom close to the fabric edge.
Step 4: Construct & attach flap
Pin the flap to the edge of the crown, making sure the ends are symmetrical to the center front. Baste.
Step 5: Construct & attach brim
Starting from one end, insert the plastic brim stiffener inside. Pin lengthwise, tight to the inside edge of the plastic brim piece, so that the pins are pointed to the left with the heads to the right. It doesn't matter if the seam allowances inside go on one side of the plastic or one on each side, but try to keep it consistent the whole way or you may get an Unsightly Bulge. Pull tightly so the fabric is a little bit stretched, rather than potentially saggy.
Pin the brim to the front of the hat, matching notches, over top of the flap. Sew it down along the pin line, removing the pins as you come to them.
Step 6: Inside band
Pin the band to the inside of the hat edge, folding the first end in to make a nice edge when it's done. Stitch all the way around, keeping on the fold of the bias tape for a tidy edge. Tack the ends together on the side not sewn to the hat so they don't flop around.
Fold the band to the inside and topstitch all the way round the hat, making sure not to catch in the flaps (or brim, but that would be difficult).
Step 7: Add strap across front
Press the long edges of the strap piece to the center, and topstitch if desired. The original actually did not topstitch this piece, it was simply pressed hard enough to stay in place. You could also use stitch witchery or a flexible glue to keep this down.
Pin to the hat front as in the pictures. You could tack through all layers but the original was stitched only on the inside, a nice touch that I wanted to retain.
Working carefully, adjust the pins until the inside fold of the strap is pinned to the crown, but not the outside. The pictures show this better. Stitch down, a millimeter or so to the outside of the pin, to get a nice taut strap.
And that is it! Hat complete. You may now put it on and order Imperial Senators to be terminated.