If you feel ambitious and have some technical knowledge you can build your own crossbow. There are very few plans available but this one from a 1953 copy of Mechanix Illustrated is not too complicated and should produce a reasonably powerful recurve crossbow. You could take the methods used in this crossbow design and update it using modern materials and techniches. You Tube is full of ways of making crossbows from anything from paper to Lego to pens but nothing about making an impressive powerfull bolt firing crossbow.
Simply click on the images, download them to a file and print out.