If you don't have enough fat for a Brazilian but augmentation, there are actually two options that might help you accomplish the desired results. The first one is to gain weight. Typically, I recommend patients to gain at least 20 pounds prior to surgery. This will be enough fat to sculpt your buttocks and make your buttocks look bigger and with a nicer shape.
The next option is use a butt implant. This is a viable option to augment this area. The fact is that any time you put a foreign body into any part of the body, there is always the risk that the implant might be rejected or get infected among other things. But implants are not typically performed by most plastic surgeons. For this reason, you need to consult a plastic surgeon who routinely does butt implants. Now, I always inject fat with a butt implant because the butt implant increases the size of the buttocks only in the central part. As a result, it does not help blend the hips with the buttocks.
Web reference: http://www.babygotbutt.com