I was in Tesco recently searching through their frozen fruits section for anything low carb - there were blackberries, a fruit mixture and coconut - I also found frozen avocados to add to my trolley
My lovely wife makes me individual pots of sugar-free jelly with fruit and I often have one after dinner with double cream. She adds various combinations - rasps, strawberries, blueberries, grapes. Blueberries are higher carb (9.1/100gm) as are green grapes (15/100gm) but a half dozen or less of either don't really add to a lot of carbs, and I know from my meter that any impact on my BG is minimal.
I find strawberries, raspberries, blueberries and blackberries are fine. They work best for me in the middle of the day, and if added to my evening meal do cause a rise in BG, but not severe. As always your meter will tell you!