is it possible to make my own bucket seat
Yes.
I'm planning this out and am going to use a piece of 16 gauge sheet metal.
First step is to get a tailor's tape measure. These can be had at walmart for less than 2 bucks. It is a flexible one, meant for going around contours and such. Measure yourself! Measure from about two inches from behind your knees to the tailbone. Then measure from the tailbone to the C7 veritbrae. This is the one that is between your shoulders and points out a little at the base of the neck. Mark this number down.
Next, measure from one hip around your butt to the next. Add a few inches, about 3-5 depending on how bucket like you want it to be.
Now, get your piece of material, metal in this case. Mark a spot in the center. This is your center point area, which is roughly where your tailbone will point to. Now, mark a center line going from this out as far as you measured for the back or for you legs and vise versa. You should have your center point, and a short line for the legs and a long line for you back. Next, perpendicular to this line, mark another that is your hip measurement. Now, draw rounded out shape that connects these lines together at their end points.
Cut this shape out. Cold chisel, jig saw, recipricating saw, band saw, plasma cutter, oxy-acetyline, take your pic. Deburr the edges if necessary.
Now, get a stump with a hollowed out section or something else as suitable and a hammer. Begin to hammer the metal at the center point going along the lines you've made. This is called dishing. It will begin to bend the metal. Just keep going this all along until it reaches the shape you want. Roll the edges to add strength and avoid cutting yourself later on the edges.
I got this idea from making armor. Here are some videos that show dishing and rolling.
http://www.youtube.com/watch?v=-tL-pSRbq4g
It making armor, but the same process is used in this method. This is how I plan on making my seat. This method also requires a little practice.