You don't have to do HRT to solve the specific problem you describe.
I got an E-String, which delivers 2mg of estrogen over a 3 month period, specifically to the targeted area. It is used for vaginal thinning and dryness issues and according to my doctor, even patients who have had cancer are allowed to use it. Of course, some estrogen does get into your system, but very little in the scheme of things. In fact, it takes almost the whole first 3 months for the tissue to build up. You pop a new one in every three months.