Those are really your only options if you don't have more cash to put down.
Appraisers can be idiots, so if everyone involved really believes the house is worth more I'd get a 2nd appraisal (work this out with your lender as well as the seller).
The burden is really on the sellers at this point. Their asking price didn't hold up. That's why you have appraisal contengencies in your purchase agreement.