I got some at the post office - THOUGHT I was getting the FLAT RATE Legal Size Priority Envelope.

It wasn't.

Be sure to check to make sure that whatever you get says FLAT RATE somewhere on it if that's what you think you are getting - otherwise there may be an unpleasant surprise at the post office.

I was looking again last week and they still didn't have any of them..

My post office said they have to be ordered. Don't know if that applies to all post offices or just mine.

Go on line to the USPS site and order them. It will probably take a couple weeks but they will deliver them to you.

I like to get the padded flat rate envelopes as my post office will no longer accept the flat rate envelopes if they are holding anything but documents. I order them online and it usually takes about a week to receive them. I order them in sets of 15 :)

We made the mistake of using a regular priority and not a flat rate. Only make that mistake once. It was costly.

I have learned my lesson too. Just ordered some priority envelopes from US Post Office. Now I will have several ready to be used, plus it sure saves on gas. You can go online and schedule envelope pick ups also.

I send everything UPS. I know it is a little more expensive, but I send it through my work and we get a large discount and tracking actually works. I will pay extra not to have to go to the post office. The line is always a half hour long.

FYI-
Just in case you wanted/needed more, you can call the 800 number to get your account changed to a business account.
(I'm not sure you if you can do that online).

An eBay ID (or etsy one, I'm sure) is enough to qualify.
Then you can order 100 envelopes at a time.

Sadly, there is no middle ground - it's 15 or 100.

I live in a very small town..our postmaster has me order the supplies for them..he said they won't send them to him at the post office unless they do a certain volume of business each month..but I can order them using my eBay name as a business. So if you only need a few and your post office doesn't carry them you could always donate your excess ones to your post office. I am sure they would take them.
Happy Stitchin' crafty_linda_b