Hey, it could have been worse; gunsmiths used to occasionally embarrass themselves when trying to remove a barrel from the old Norwegian Krag-Jorgensen rifles – it too has a left hand thread.
If all else fails and you decide you’re willing to destroy the pedal to get it off - try the same trick that gunsmiths use when trying to remove a really stuck rifle barrel (in addition, of course, to turning it in the correct direction!!). Take a hacksaw and cut a shallow groove around the entire circumference of the pedal shaft as close as possible to the strut that it’s screwed into. This relieves the side pressure and makes it much easier to unscrew. (I’m assuming the pedal doesn’t have a pipe thread – I don’t think it does.)
Actually, you might not have to cut the entire circumference depending on how the strut and pedal shaft are joined up. Also, a Dremel tool with a cut-off wheel or even a triangular file could probably be used in place of the hacksaw.
I could be wrong, but I don’t think you’ll have a problem finding a replacement pedal. Wal-mart probably has them. However, I’d locate a replacement pedal before gleefully destroying the old one.
Good luck!