Thank you all for the guidance, I found the frozen purees at the A&G (on sale!):

In this photo, they are thawed and ready to be mixed with simple syrup.
They did not have cherimoya, but did have something that looked familiar, guanabana-- also known as soursop--turns out they are in the same genus, but different species. I also went for passionfruit, something I had wanted to try. The sorbets turned out great:

The passionfruit is bracingly acidic-- I think it would be good mixed with a low-acid fruit (mulberry??). My daughter loved the
soursop, which had a great tropical flavor. The sorbet is very easy-- I adjusted the amounts because the recipe originally called for 3c fruit pulp, but each package only had 2c. For 2c pulp, mix 1/2c water and 1/2c sugar, heat to dissolve and, once dissolved, cool. Mix the fruit pulp, sugar water, and 2Tbsp lime juice, then chill. Freeze in ice cream maker. (Or maybe in popsicle molds...).
Thanks again LTH!
Jen