I just left Bali after two months, so I guess the right person to ask

All common topicals were available entire time while I was there. Durian, mangosteen, rambutan, mangoes, salak, dragon fruit.. Season is coming to an end now. Actually it was not suppose to be peak fruit season but ever shifting monsoon patterns make it more unpredictable. October was extremally rainy in Bali, while it was supposed to be dry.
Indonesia is not the place for durian hunting. Very unpredictable quality. Sellers buy entire tree harvest in advance from villagers and instead of making multiple trips to a tree, cut lots of underripe fruits and take everything to a market at once.
Now I'm in Western Borneo, it's suppose to be peak fruits season, but limited selection available. For example, no marang, even though they definitely suppose to be in season if you go by old patterns. I was told they finished few months back. Dabai just found only one person with overripe fruits, season almost finished. Less common jungle durian varieties no where to be seen. Although you do have quite a few local only exotics available now. I just don't think they are worth travelling for ( I did not come for fruit hunting. I tasted everything before ) Unless you have intel on the ground, it will be difficult to time everything properly simply going by previous patterns. Eastern Borneo has different patterns.
edit. forgot to add, last day in Bali got contact of man who say he knows super tasty red flesh durian in Java. But not season now. The place is very close to Bali. From Bali to Java one hour ferry, and than one hour drive to tree. He will keep me updated.