You can purchase a replica Spartan helmet at a store like Museum Replicas, however, if don't want to spend a lot of money, consider making your own helmet. You can make a Spartan helmet for very cheap, using just cardboard, tape, spackle and paint. The best part is that you can choose the final look of the helmet by sanding it down and choosing a glossy, new finish or by giving it an aged finish as though the helmet were found in an archaeological dig.
Build the front piece for the helmet. Look for pictures from the movie "300" for inspiration and draw a template for the front of the helmet. Make sure it is life-size and then transfer template to cardboard. Cut out the template and cover the edges with masking tape so that it doesn't bend.
Make the helmet "hat." Take a tape measure and measure the crown of your head. Using a strip of cardboard a couple of inches in width, cut it to the length you just measured for your crown. Tape the ends together. Make a dome for your crown. Take another strip and attach one end to one side of the crown and the other end to the opposite side of the crown. Take another strip and repeat so that the strips form an "x" shape at the top. Finally, measure and cut four triangle pieces of cardboard and attach them to your hat so that they completely fill in the dome of the hat.
Create a rim for the helmet. Studying the pictures of the Spartan helmet you'll notice that the helmet has a rim at the back. Build the rim using a strip of cardboard 2 inches wide that you attach to the back of the helmet. The rim will go all the way around the back of the helmet, stopping at the point where the front piece attaches.
Attach the front piece of the helmet to the hat using more tape.
Texturise the helmet. Cover the entire helmet with spackle and allow to dry. Once the spackle has completely dried (allow at least 24 hours) lightly sand the surface.
Paint the helmet. Begin by spraying the helmet with a primer. Once the primer has dried, spray the helmet with a copper shade. Finish with a layer of gold paint.
For a newer finish sand until you get a very smooth surface. For an older look, only lightly sand the helmet so that it still looks "pitted."
Don't forget to cover the edge to fhe front piece with masking tape to keep the helmet rigid.