> Sadly, you cannot, from what I can tell.
I have heard it claimed that they are not DOT compliant which prevents them from being sold to the public, so USPS crushes them all at the end of their life.
That said, once in a great while a non-USPS LLV shows up on GovDeals. Last one I saw was local to me a few years ago and it sold for over 10 grand.
"I have heard it claimed that they are not DOT compliant which prevents them from being sold to the public"
For the very small bit of time (as you mentioned) - the Commercial Long Life Vehicle, or CLLV: https://www.flickr.com/photos/hugo90/33789231153