Hi Daisydai,
I don't think mulberry sells the East-West Baywater anymore. You may be able to get them at the secondary market such as eBay.
Here in the US you can buy M bags via the M website and call the nearest Mulberry store. I suggest the latter, when you buy direct via the website you get charge custom taxes and ver impersonal. Plus it's just nice to call your nearest M store and develop a nice relationship with an SA.
The nearest Mulberry store to me is in San Francisco and my SA is Eugene (I am totally pleased with his customer service).
Happy hunting!