The words "natural and organic" are greatly abused because we use them interchangeably when we SHOULD be saying healthy, attractive. While it is natural for all skin to age and for all breasts to deflate and sag, I seriously doubt that THAT is what you want when you go to a plastic surgeon.
Your comment "I fear risk of leaking implants." is extremely important. If you are unwilling to take the chances of a car accident or a plane crash, you have no business getting into either a car or a plane even tough the likelihood of this happening is VERY small. Similarly, you must accept the fact that EVERY BREAST IMPLANT WILL FAIL AND LEAK. This may happen the day after surgery or 25 years after the surgery but the implants will not last forever. if this fact bothers you - do not have the surgery.
The Allergan/Inamed/McGhan 410 is a stiff silicone gel implant which is not widely available for use in the US. Its Mentor analog is the CPG implant. These textured, tear drop implants are filled with a form stable SOLID silicone filler. All other silicone implants are filled with a "cohesive" very sticky silicone gel filler and usually come in either tear drop or round, smooth or textured implants with various degree of projection.
You are asking for a reasonable result. Australia has a LOT of good Plastic surgeons which could give you this result with just about ANY breast implant (BUT is cannot be "organic", "natural" etc)