You could try a ratchet with a deep socket and see if that works.  Also, you
might try to tighten it, then loosen it.  Sometimes that works, too.  Will
the tire hold air?  Can you inflate it and drive to the shop? (Be careful of
it blowing, though, since it's sat flat).  Or, you could have a mobile tire
shop come and do it on-site.

Leverage may be your key.  Can you fit a long metal (hollow) pipe over the
manual tool?  The extra leverage will probably work for you.  I've done this
before, too, but using a deep socket and ratchet.