These are the ones that I bought over 5 years ago. They claim 10 year life and I have no doubt of that.
https://www.supergelproducts.com/breast-forms-palsbreastforms-nipples-trl3.aspx
They are a soft silicone. They as not quite as soft was the liquid gel, but unless someone is squeezing your boobs, no one will notice. But, since there is no skin and seam, you can do whatever. I sleep in mine most of the time. Their “lightweight” models are lighter than mine and softer, but you get what you pay for.
I notice the price has gone up a bit. I think mine were about $220 at the time. Previously I ruptured 4 pairs of regular ones in less time than I’ve had these. At $80 per, the cost avoidance covered the price of mine. The surface is also slightly tacky. With a reasonably close fitting bra, they will stay in place. You can’t go braless, but they behave more like real breast tissue in the it is effectively attached to your body.