I really sympathize with your plight. Lands end used to make a really great soft cup bra with convertible straps. in 38A it fit my frame perfectly, and at the time I was wearing Amona size 4 651 breast forms, with fit perfectly. Luckly, I bout several extra as the discontinued their "best selling" bra and all lingerie within a year. .
Only had one other bra style that I really liked and it was a warner 2516 (totally different from the current model) which also was a soft cup with convertible straps. Unfortunatly, it was made in the early 80's and has not been made for years. ..
As someone above said, when you find one you like, buy several as they will change styles. .
My big issue, especially with forms is the "molded cup" and anything padded. . .It is as if they were bullet proof. I like to feel my forms bounce a bit and like to reach under my shirt and feel the softness of the matter. . . with the lands end bra and forms, even my wife agreed, the felt VERY lifelike. The formed cups do not feel real or allow for any bounce.
I keep hoping for the non formed cup styles to come back in vogue!