@liong there is a charity called Knitted Knockers (Google if interested) who make soft cotton 'foobs' that will fill a bra. They are also, I've been reliability informed by a couple of close friends, a lot lighter, cooler and more comfortable than the silicone 'chicken fillets'. No use if you want to swim (apparently they tend to escape and are tragic when wet) and might not be quite as stylish in close fitting clothes.
You can download a pattern from their website if you, or someone you know, are crafty and want to try them until something more conventional.
Hopefully you can source something affordable. Mxx