If you have no luck finding the metal Adler part, you might search out a local welding or machine shop that could TIG-weld those pieces back together for you.
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Thanks...the part is small, and would require skilled work...
I will tour the local industrial park and see if anyone will take it on...

I like the idea of finding a jeweler...

I have made some drawings and am looking for someone to make a part out of a solid billet so might take this round as well, but round here in the UK such small workshops that do fabrications are unwilling to undertake one off manufacture. I found this a few years ago when trying to get a part made up for my old VW. Since retiring I have lost access to workshop machines, I could do it myself if I can use the machines.

My hope is that somewhere there is an old suitable Adler machine willing to donate the right part to me.
 

Hi, thanks... helpful information, seems the European machines are expensive in the USA, no doubt due them being uncommon compared with the Corona, Smith-Corona, Underwood, Remington and Royal (I am guessing a bit here).

I am watching the uk ebay sales...

The one you picked is the earlier type, with the non-collapsing return lever, and is housed in the 'high top' case, the early fibreglass case.

The later machines have a black 'blown plastic' case, which is flatter (no domed lid), and has the collapsing return arm mechanism to fit. These are usually £50 or so, and it is then an expensive replacement part then, and a shame to take a single part from a working machine, and have the rest languishing and otherwise one less machine available for the encouragement of typewriter users, which is what we surely not the best way to serve more typewriter use in our community.