A promising lead on ebay from a popular French brand (Comptoir des Cotonniers) that seemed to fit the bill turned out to be quite disappointing (it didn't fit properly, breast pockets were too small) and was put back to the market.
So now, after weeks of search, I feel like this perfect coat really is a chimera and maybe I should make do with:
a) the ASOS
b) the Topshop, if it ever comes back in stock
The simple fact that I'm hesitating makes me realise that I probably won't buy either. They're great but just not what I want/need and I have a hard time buying online and negative recounts on Topshop's customer service have always held me back from purchasing from this site.
Anyway, a duffle-coat would've been useful this week with all the rain, wind and cold we're having. I'll keep my eyes open but the obsession has subsided...And I think that's for the best.
In the meantime, I bought a hooded scarf from COS.