Just send it in a Postal Priority box and write “ORM-D” on it. You are not “the shipper” according to DOT regulations and bear no responsibility for its packing or certification. Even the questions they ask you won’t stand up in a court of law unless you have been trained or certified.
Wow, what a genius. USPS won’t ship it and UPS doesn’t want “ORM-D” on any box, they want a picture of a diamond with 2 black triangles on the top and bottom.