I seriously doubt you can. I think most money orders require cash just like lottery tickets and some other things.

There was a neat little trick years ago where you could charge AMEX Traveler's Checks (say at AAA) and get the miles on your card. Then when the bill came in you just deposited the traveler's checks into your account and paid the credit card bill!

They (AA in particular) wise up to this and promptly excluded earning miles purchasing traveler's checks.