Where to find a dress coat?

[tak1ngchances]

Having spent yet another year shivering at Ascot in the Great British Summer, I have decided to try and find a dress coat. Sort of just below the knee, fitted with maybe just one button on the waist. Kate Middleton seems to have a plethora of them...you know the kind of thing. See example here
I have never seen any in the shops though. Also can't find them online but perhaps they are not called dress coats?
Any ideas? Budget is £250 max. I would like a neutral colour, maybe cream.

Someone linked to this the other day and I can't stop looking at the Aquarius coat on the page - I love it. That the sort of thing?

Thank you Hassled! Yes, that's the sort of thing. But i was imagining with no collar. Actually there is one called Jasmine, also at Hobbs that is not bad Jasmine. Might be a bit plain?

That Jasmine one is just lovely. I think plain is good - you don't want it to distract from the dress/hat/shoes. I need to come up with a good reason why I need a dress coat.