Yes Jaeme, It’s a challenge. Hopefully more GI values will be published in the future. Also, one food company has validated (against actual GI values) a test method for the lab that can estimate GI values, but so far, they have not been publishing results using the method.
A decent rule of thumb is to used a GI of 50 for any foods you don’t have an actual GI value for as most vegetables have GIs ranging from 40-60. That way, at least you will be counting half of the carbs towards FP. Some people assume a GI of zero which means they count all Net carbs grams towards FP, but that seems overly cautious to me. Don’t forget to add fiber and any added sugar alcohols to the final FP.