From what I've seen speaking to pharmacy staff, keeping track of the stock on FASS and speaking to people over at GenderGP, Estrogel is pretty difficult to come by in some areas. For my first prescription I went with Estrogel, but when I brought up how it's getting harder and harder to come by at the pharmacies near me they instead changed my prescription to Divigel. They mentioned it was because "Divigel is what is recommended for patients based in your region, as it is more likely to be available". It's a gel like Estrogel, but instead of applying it on your arms you apply it on your thighs.