Bras for larger ladies

I was diagnosed two weeks ago with DCIS and IDC (stage 2 admixed), and had a wide local excision and sentinel lymph node removal yesterday.  More than half my boob gone.  Now facing chemo and radiotherapy.

What I would love to know is:  where does one buy bras for plus size ladies?  I'm a 48 DD/E and I have not been able to find post surgery/mastectomy bras in that size, like anywhere.  I bought what was supposed to be a 48 from Amazon, but I can't even get it closed.  I've been wearing these soft cotton crop top type bras, but they're not very supportive and it hurts when I walk, as the boobie wobbles lol.  Plus I can't lift my arm to get them on!

If anybody had any suggestions I would be eternally grateful - and so will my poor boobies lol.