Postal money order?

Cope said
How does that work?
I cash it before sending the part or....?

Yes, wait until you have the MO, and as said above if your local PO has the funds available to cash it, go there cash it and ship the item.

As also was mentioned the MO number will be in the USPS system and you can verify it's authenticity, if you so desire.

I have never had an issue with a USPS money order, I would shy away from any other type MO though due to the many cases of fraudulent money orders..