The only reason I can think of why anyone would need a key instead of just a simple toggle switch for a snowblower would be to keep kids from accidentally cranking it up. Got any kids? If not, just keep the one key that came with the thing in the ignition switch. Permanently. If you don't take it out, you won't lose it, and you'll never need a second key.

If you don't think it's okay to leave the key in the switch, use a lanyard to tie it to some part of the machine. Make sure the lanyard has enough slack so the key can be inserted into the switch, and don't ever untie it.