someone should 3d model them so you can just get it cnc machined from aircraft aluminum and forget about it
i know people would pay. i probobly would
when I had to fix the one on my RF amp (or was it function generator?) I thought I would pay like 300$ for that part if someone had it 
But I ended up doing a splint with a piece of mild steel and 5 screws.
getting that part is similar stress relief to going through 20 bottles of alcohol
I did find them but I know i will curse myself in a few years if I do sell it because a good current source... might be forever. And it could get adapted to other frame with some work
The 2 side panel covers are for a counter, which I imported from the USA, they don't exist in the UK any more, sellers destroy everything for a few glass parts and throw the rest in the trash, before listing them on e$pay, they don't care if it's the last one in the UK.

Also I've not found anything useless that uses that narrow case and can't justify scrapping usable or working TE to take the parts. It's not the only counter I have with missing covers, I've found some of the counters use unique sized top/bottom covers too.
If you want to keep them for something else that isn't a problem, just let me know if you change your mind, doesn't matter if that is years later, I'm quite patient.
The cracked frame I have is also one of the small amplifiers, though mine is the pulse version, very similar looking to the RF amp. Maybe I can straighten & join that one.
where am i?
USA, this is not really an issue for me, I have ways to get stuff that ePay sellers don't want to send international.
Re: the wiring one HP current sources, I used to own a late 6186C (300V 100mA), the main PCB was hardwired in that, no connectors for unknown reasons, that one I sold some years ago, which I now regret.
But I solved that by buying a cheap & poor condition 6186B to repair, it's the one with the messy main board, which I posted some pictures of in your transistor tester thread, all those random unmarked transistors & other added parts are now removed.
To make this one even better, they lost the boron nitride transistor insulators & put more heatsinks on the back of the unit, which are live at high voltages.

I don't think they make those insulators anymore, but maybe others in ceramic are available, I've not looked yet.
I noted you asking about the TO-39 heatsinks for your 6177B/C? Seems the 6186C used one, but the 6186B doesn't need one, no idea why.
David