Should take the B10 blank, still readily available in the aftermarket, as Marty stated, anyone that cuts keys should have them. OEM Briggs & Stratton B10s are also available from several vendors and Ebay as repop and NOS items relativley cheap, if you want an OEM key.
If you don't have a key at all, any locksmith can make you one. Just take them the lock cylinder from the ignition switch.
