There are several low protein foods that you can give your baby.
Just make sure that whichever food you pick does not contain any red meat like lamb, beef, venison, etc. and that it's mostly vegetarian with no more than 21% protein, preferably 18%, especially just after surgery.
A couple of foods are:
Avoderm Vegetarian
Natural Balance Vegetarian
Also, if you join the liver shunt/mvd group, there are several other foods mentioned there that members feed their liver compromised dogs. And there are recipes for homemade diet formulated by vets for long-term use that you can cook once a month and freeze into little baggies and take out every couple of days.
Are you giving any supplements? The prescription diets like the RC Hepatic LS 14 has increased amounts of zinc and other vitamins/minerals that their bodies need at this time, so if you're going to feed a non-prescription dog food you might look into giving a supplement like s-adenosyl-100 which contains denosyl, milk thistle, vitamin b-complex, zinc, etc (all beneficial to the liver).
And I'm so glad that you're baby came out of surgery okay!!
Also, I wanted to add that if the Petsmart near you has a Banfield, you can buy the RC Hepatic LS 14 from them. All you have to do is get a prescription from your regular vet and take it to Banfield in Petsmart. They will put you in their system and give you a prescription card that you can use anytime you need to buy the food.