Where can I get a breast implant sample?

These are medical devices that are not for sale to the public, Having said that, I have occasionally seen samples for sale on Ebay. I do not know and I do not want to know how they got them. You can view samples in a surgeon's office (not for sale) and there are sizing kits available that provide imitations of  these.  See Breastimplantsizer.com

Before undergoing a breast augmentation, you should read about the risks and benefits of the surgery and the various implants. You can order a pre-consultation kit from Natrelle.com where you can try various sizes, but this will not let you actually feel the real implants.

During an initial consultation, I allow the patient to see, feel and try different sizes and styles of implants so they can make an educated decision on what is right for them. Remember to consult with a plastic surgeon that is board certified by the American Board of Plastic Surgery to ensure he has had the appropriate training.

Most plastic surgeons have breast implant 'samples' in their clinics. I use them to help patients decide what size implants are right for them...schedule an appointment with a board certified plastic surgeon. You'll be able to handle the devices and appreciate the difference in weight, texture, and folding between saline and silicone implants.

You can get a sizing kit from Allergan but in no way do the implants feel natural. They are basically small bags filled with water.

Breast implants are regulated medical devices and as such the FDA will only allow them to be sold to physicians for implantation. Most plastic surgeon offices will have implants for display but few will let them out the door with a patient. They are hard to come by for display.
Natrelle sells a kit of 4 water bags in different sizes along with a bra with pockets. I've had one patient use the kit and it seems more confusing than anything else. I was lead to believe it contained defective implants that could not be sold but the water bags are a pretty poor substitute and the bra is pretty flimsy. You would do just as well to go buy your own bra and use zip lock bags and water or stockings and rice to make your own "implant."