MYA sell bras themselves, I bought two for £65 which includes postage. Good quality for the price paid especially when you need to wear them up to 8 weeks post surgery.
They are cotton bras and fasten at the front with adjustable straps. Really comfortable too.
I just called the MYA clinic I was with and you can order them over the phone, they will help you with sizing too they do sizes from small/medium/large rather than cup sizes x