Yeah, that shipping box looks much too small for a rack mount scope. Especially for some thing as heavy as HP. Was there ANY padding in it?
Padding at the sides and around the brackets - Poor but better than nothing.
Padding at front, rear and top and (fatally) bottom - virtually none.
Some more unpacking pics. This one:

Shows ALL the 'padding' that was underneath the scope. The outer box, a thin cardboad box flat (about 3mm) and a few layers of that very thin foam sheet (maybe another 3mm total.)
A miserably inadequate, stupid, incompetent job.
The seller's listing text said "The unit will be heavily protected to prevent any damage while in transit."
Also I'd asked them to pack extra safely for international shipping.
Every now and then I goof, and actually believe what people say, and forget that the word is full of idiots.
I would NEVER ship a heavy instrument via the US Postal System. First, they're too expensive. Second, everything heavy that I've ever shipped with them has been damaged. The USPS simply isn't equipped to deal with anything bigger than would fit into a mailbox or that you can carry in one hand.
US shipping was with Fedex. Who in my experience are overpriced oafs. But with ebay sellers you get the shipping they choose.
The stupid - it hurts! WTF are people thinking when they pack something like this?!? (Yeah, I know - they are incapable of thinking - fucking morons.
) That poor CRT is well and truly destroyed. 
It infuriates me to see old gear ruined by blatant incompetence in performing an action that should be so simple. Cushion and immobilize the instrument within a container a few inches larger than it is. Why is this on par with rocket surgery to so many people WHO SELL SHIT THAT MUST BE SHIPPED AS PART OF THE PROCESS? You had ONE JOB!! 
This is about how I feel too. Except I'd add more profanity and assassinations by Ninjas.
Over the years I've been bringing stuff in from the USA I've seen some unbelievable incompetency. Stupidity no one would believe without seeing photos. For that reason long ago I started taking detailed unpacking photos. Result: I have a large collection of 'packing fails' (and success) pics. I haven't updated my NoBlog since mid 2020 (Wife passed away plus the unrelated but also depressing covid global insanity) but I'll start again soon. One I've started writing is 'packing parables.' Kind of a do's and don'ts of packing/shipping. It might be useful as an education for the packing-naive. The people who seem to not understand impact absorbtion, G-forces, etc.
Fingers crossed you can find an acceptable replacement at a reasonable price.
Sadly the Australian guy with a NIB one, thinks it's a hot item and will not budge on price. "The only one available!" etc. He's had it listed for several years. I think I'll hunt around a while. Vint-HP may turn up something.
One area of concern is that this tube has a very early kind of flexible PCB hanging off the front, serving as connections to the front meshes. I see in mine, that this flex-PCB is completely delaminating and falling apart. The tube would not have worked even if it was intact. Question is, maybe even a 'New in Box' one will have the same problem. It looks like some hack could work, but I'm not sure yet. It _might_ be that HP 181A scopes are hopeless cases by now. The manual was printed 1971.