Can anyone recommend a complete, moist hypoallerginic food that's easily available, for a dog with chewing problems?
Thanks for any suggestions.

Not moist I don't, several kibble ones that can be soaked. Does your dog have trouble with the mouth or the digestion that the food needs to be soft. Most dogs can cope with swallowing kibble whole if they lack teeth without causing any trouble at all.

Chappie is a good complete moist food but not sure if it meets your other requirements, very good for dogs with gut trouble and not bad at putting the weight on either.