If you don't want to scroll all the way, the filter buttons are really helpful (imho). Just checking the backpack button would reduce the long list to only a few items which are easier to handle.
If you're not seeing the gadgets, it is possible that you run into the overflowing vendor bug. If Annas stock is full with arrows/stones and nothing else, try to buy away all those ammo. I've heard that items which she actually has in stock don't show up if the list is crammed with ammo.
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