Diet Recommendation for Diabetic cat with Megacolon

This is my first post, althought I have visited the forum many times and learned so much! Our male 8 year old cat was diagnosed with diabetes 18 months ago, and it has been a challenge. He has been on 20 units 2x daily of Humulin N for the past 8 months. The past few months we have transitioned him from Hills w/d dry to a primarily wet diet. We started with the Fancy Feast varieties suggested. Currently he has been eating By Nature and Wilderness wet, with a little Taste of the Wild dry food to encourage him to eat on occasion. Two weeks ago he became constipated, started vomiting, and quit eating. We had to take him to the vet twice in one week for enema and stool removal. Luckily, he seems to be on the road to recovery, but the vet advised eliminating all dry food, and adding water to his food, which we had already been doing. Vet also said we need to add some fiber back to his diet. We have had some luck with pumpkin and baby food squash.....is that enough, or do we need to look at another variety of canned food that contains other fiber sources? I understand Megacolon can be a recurrent problem.

Thankfully, Spooky is almost himself again, and his blood glucose curve was good today with just 15u.

Would appreciate any advice on feeding to keep things 'running smoothly' without blowing his BCG!

Kelly & Spooky