Have you checked Ebay, Catrin? I have found some good deals on sports bras there (not front-closure, though). Good sports bras are so expensive, I only buy them on sale. I am lucky to be small breasted enough that I can wear the cheaper ones with more typical sizing, but they do go over the head, and I get it about your shoulder. That certainly complicates things.
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow