The itching is a good sign of healing going on. It is normal. Keeping the area moist can help the itching sensation. But it does not sound like your doc recommended anything post-op other than the shampoo?
I have heard from various patients over the years that "baby shampoo", specificallly the product made by Johnson & Johnson, can promote the itching sensation.
Try contacting your doc for another product that he may recommend.
Just be careful not to scratch your sutures or the recipient area.
Independent Patient Advocate
NOTE: I am not a physician and not employed by any doctor/clinic. My opinions are not medical advice nor are they the opinions of the following supporting physicians: Dr. Glenn Charles, Dr. Jerry Cooley, Dr. James Harris, Dr. Bob True & Dr. Bob Dorin