I was browsing through RoseGal's collection and found this loose fit coat on sale for $15. I'm not sure about the quality, but the coat looks great and super stylish on the picture, and it's a risk I'm willing to take at this price.
To be exact, the coat is $15.01 ... and it comes with free international shipping. I have also found a bag on sale - the "Vintage Style Solid Color and PU Leather Design Women's Crossbody Bag" for $18.78, which would go well with the coat.
If you like the trench but you're not into the colour, check out the Women's Stripe Cardigan Long Sleeve Cotton Coat, which is available in S and M for $16.81.
I think paying $15 for a coat delivered is hard to beat, not even Boohoo comes close to this. In fact, I have seen similar coats for $40 over there (with free shipping), which is over double of what you would pay at RoseGal.