This online store is also Tracey G . https://www.themastectomystore.com.au/product-page/amoena-sew-in-bra-pocket-191  ;

  I did it once, 18 years ago, but i sewed it in too tight  top and bottom and had to redo it. The top edge that meet the clevage section  actually needs to 'bulge' and show ,as a natural breast mound would.No bra fully encloses a breast and therefore not a prosthesis. But I remember when i first started wearing it was self consious  of it showing. Until i learnt , as a C then D cup, it has to show, so being covered in fabric in a pocket is OK. After those first few attempts ,i started invested in pocketed bras.But they can get  very expensive for good well structured ones.

There are a couple others who also do online zoom consults, Erilan does,www.erilan.com.au

 You can also go to the Amoena website and search for distibuters, they are far and wide and not all are equally good, so worth a drive if you can get to a good one. ( department store ones seem to not be as good as the rare specialty stores)

If your near Woollongong i can recommend CasaMia Lingerie for masectomy bra options and an in person  fitter , make appointment.