No, I've never heard of them being in Europe. North Africa maybe, with the Aussies. But not Europe.
Crete is the closest to Europe you'll get where the slouch hat was worn.
The Astralians and (i think) kiwi's wore them there.
http://neoskosmos.com/news/sites/defaul ... ldiers.jpg
ANZAC and Greek troops shortly before the Germans attack.
Edit: thats actually a lie... the Australians wore the slouch hat on service in Greece, which is considerbly closer to Europe than Crete and they did a bit of fighting there too.....
However I cant see anyone running a 'Greek Front' battle in the near future and its definitely not NWE so you're probably better off shelving the slouch hat plan (and TBH you could get so much more really usuable kit for the price of a slouch hat... my repro was over £35 quid!)
Edit 2: Christ, i just re-read that OP, 'Eastern Front' (did you mean Western Front?) cos I cant think of a worse piece of headwear to take with me to Russia!
"I think we are in rats' alley - Where the dead men lost their bones."
love 'em - i bought mine when i was in OZ. As my cousin commented when I accidentally dropped it in muck there 'there not a real one until, you've got s*** all over it!
I'm a hero with coward's legs.