Spuddy it is bit depressing but I had feeding issues with previous son and similar lopsided-ness and it corrected after stopping bf! Well done for keeping on and not just stopping for vanity's sake- feel proud not embarrassed (if you can muster pride). That is after all why nature gave us 2 boobs, back up in case one doesn't work!
You could try one of [http://www.amazon.co.uk/gp/product/B000YQNUMA/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=103612307&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B000YQPZQ4&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=1ZTMXDEHTQHX6PYXHPZX these] - you just choose s, m, l or Xl. They support small and large norks - I bought mine for pregnancy/bf but still wear them years later, even though my boobs are a lot smaller, because they are so comfortable but more supportive and shaped than a crop top thing. In fact they now come with a kit to change them into a non-maternity bra so other people must agree with me!
Work out your correct back size, guesstimate the cup as best you can.", then go up through the cups until you get to the one that totally contains all your beast tissue. Brands like Ewa Michalak supply their bras with removable pads to help with symmetry issues.
You are right about the body confidence aspect. I look awful. i never had nice tits anyway (tiny fried eggs!) but at least they matched - now i just look freakish. I loved my pregnancy body but i hate the way i look at the moment.
DP made the mistake of laughing at them the other day and i burst into tears I'm usually humorously self depreciating, so he he was really shocked and felt awful he had upset me.
Ha ha I actually have this problem myself as am bf and one side not working much anymore! Doesn't do much for the body confidence!!! Fit to the larger cup otherwise you could have seams rubbing and get blocked ducts, and I pad out other side with a washable breast pad or pad from my bikini!!!