Hi, Ian...
To answer your second question first, I believe steel helmets were taken on board certainly the larger German aircraft during operations.
To answer your main question, you would really need to provide some more information if possible. I imagine there may have been a few German airmen with the name Strudel. So, your first port of call might be the local newspaper, or it's present day successor, and see if there were any reports of aircraft downed in that area. There may well be a good number, so it might be a long process. You would need to determine what date and type of aircraft may have been involved.
You could also search the Aircrew Remembrance Society's website if you already have an idea of date and aircraft type. If they have a record of it logged, you may be able to match the name on the helmet with the details on the website.
I'm not sure if I would be able to assist you further, but I'm sure others on this forum may well be able to if you can provide more information. Good hunting!
Regards,
Paul