There is a shortage of Ovestin at the moment, which is the 0.1% estriol cream. If you have been prescribed the weaker generic Estriol Cream at 0.01%, there is no reported shortage of that, so they should be able to order it in.
You can apply an emollient such as Hydromol or Epaderm to the vulva instead of coconut oil, which in my experience doesn't last very long. Alternatively you could look at the Yes products on their website, or you can buy Sylk otc. There are so many vaginal moisturisers around that it comes down to personal choice in the end.
JP x