You can remove the freehub with a 10-mm hex wrench, then use a torch and brazing wire to braze the internal parts together.

A better option is to buy a formula hub (about $45) and rebuild the wheel. It'll take a few hours if this is your first wheelbuilding experience, but it'll be worth it in the long run.

Edit: before you braze the freehub, be sure to soak it in solvent to remove the grease from inside, otherwise the brazing won't adhere to the metal.