If your strapless is 30D and it fits, you can try a 28E slightly padded bra. I know it sounds stupid that a 28 would be less constricting than a 30, but here is why:
The way bra sizes are calculated is a bit dumb. It tells you how long the band is when it's lying flat on a table. Except when you put a bra on your body, it stretches: fabric much more than silicone. So when you wear a normal 28E bra, it's on average as tight as a 30D strapless. It should stay in place, but it's made of softer fabric, so it shouldn't hurt you the way those damned silicone straps under the band do. I'm not saying it'll work 100%, but I'd give it a shot next time you're in the fitting room.
As for the wire (it might also be plastic?) under the silicone: cut it out. You don't need it. It's sometimes useful for extra support in bigger sizes, but in a 30D, it makes no sense.
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The way bra sizes are calculated is a bit dumb. It tells you how long the band is when it's lying flat on a table. Except when you put a bra on your body, it stretches: fabric much more than silicone. So when you wear a normal 28E bra, it's on average as tight as a 30D strapless. It should stay in place, but it's made of softer fabric, so it shouldn't hurt you the way those damned silicone straps under the band do. I'm not saying it'll work 100%, but I'd give it a shot next time you're in the fitting room.
As for the wire (it might also be plastic?) under the silicone: cut it out. You don't need it. It's sometimes useful for extra support in bigger sizes, but in a 30D, it makes no sense.