yes if it is emergency

I think the original one is better. However, if you run into some emergency, scanned one or fax is fine. I did that with mine when I have to catch deadline and it was accepted without any problem.
I suggested you getting original one since it will give INS officer no reason to doubt the authenticity of letters. You can have them fedex overnight. You have tried so hard to get letters that some extra money and one extra day on fedex is nothing to compare with. But if you really can't get that due to emergency, fax or scanned one is acceptable.
Good luck