I'm glad that you're blood tests were clear, but it must be very disappointed to be dismissed like this. No recommendations re another GP, I'm afraid, but you could try contacting the RACGP (Royal Aust college of GPs) and asking for contact details of any GPs with a dermatology special interest in your area. That way you wouldn't need a referral from your GP, and if the specialised GP felt it was appropriate, he/she would still refer you to a consultant.

Keep pushing for diagnosis and treatment, it is not normal to have itching that drives you up the wall, and you deserve to be treated better.

edited:Just found this website : http://bjchealth.com.au/our-team/our-doctors/ Dr James Choi has Immunology and Dermatology special training, which sounds ideal. You can get this issue sorted, and then decide later if you want to change from your regular GP for all other aspects of your health, or not.