I recommend you check out the app from Monash [1]. It’s a paid app but really worth it and its been incredibly helpful for me (I say this as a user, not affiliated with them). AFAIK it contains the largest number of tested foods and they keep adding new foods and retesting and updating older food quantities and list out the specific fodmap associated with each food. From what I have found online, every other source is either outdated or mostly copies the data from here.

ICYDK (From the studies I have read online) Researchers from Monash were the first ones to identify low fodmaps and they continually release research studies in this area.

To answer your question about chickpeas - right now I see 2 different tested versions in the app - one is Canned chickpeas - this says quarter cup (42g) should mostly be fine but half cup (84g) contains moderate amounts of Oligos-GOS (one of the fodmpas).

Green bell peppers - 52g should be ok but 75 to 80g contains high amount of sorbitol.

The app uses a traffic system (red, blue, green lights) to indicate the quantities

[1] https://www.monashfodmap.com/ibs-central/i-have-ibs/get-the-...