If you have Cherimoya rootstock, you can graft the Reticulata scion on it. I am in Hayward and I graft before. You can graft many different Annona varieties on the Cherimoya rootstock.
I have these varieties were grafted on the Cherimoya rootstock.
Sugar Apple
Rollinia
Reticulata (Not doing so well since I don't pay attention to it)
Soursop
If you are interested about the tropical plants are growing in SF bay area. You can join the Facebook group name (San Francisco Bay Area Tropical Fruit Growers). There are many people are growing tropical plants here. Check it out.
Good Luck
Happy Gardening.