Take a look at Digikey.com and find a MOSFET in a package with a tab mounting (like a TO-220). Look for Suitable Vds (300V to be safe) and low Rds on. Buy a big heat sink for it. Calculate the heating for full on; if its higher than 5-10W you might want to find a lower Rds on FET. Find a MOSFET driver to drive the gate. The driver chip makes the FET switch quickly reducing heating. Make sure you drive the gate with at least 12V. Find a high current diode with a fast switching time; I'm not a motor drive expert but one of my coworkers who is says that switching speed on a diode can often be more important than low voltage drop.