Hi babes I’ve also struggled with this question too. So here is what I’ve fount….
Asda do a “post op” support bra section at a really good price.
Debenhams also do good sports/support bras also.
Because I’m having a 450cc E cup I’ve fount that I needed to buy more expensive supporting moulded bras (not the tank top style) so I paid £25 for a good supporting bra from bravissimo and I brought a shock absorber for £22 from amazon.
I did buy two of the “post op” bras from Asda to sleep in at night.
I hope all this makes sense and helped a little xx