Has anyone had success getting Dr's to add testosterone to their hrt prescription?

It is certainly available as an implant. About a year and a half ago I was asked by my new consultant whether I wanted a testosterone implant put in with the oestrogen. I refused as I had tried it in the past (30 years ago) with no discernible difference.
As paddyann says your best bet is to ask for a referral to a menopause clinic, alternatively a gynaecologist specialising in menopause.
There used to be a site called Dr Foster which listed doctors and their specialisations. See if it is still going.

You ask for a referral to your nearest Menopause clinic .Most areas should have one .Since my lovely Gynae guy went back to Greece because of Brexit my new nearest is in Glasgow which is around 20 miles away.If you dont ask you wont get .Good luck with it