I am looking for another form of fiber for my dog. Any suggestions?

Hi,

My dog is not overweight, he has a nice trim waist and no belly fat. I walk him at least 1 mile a day and usually more. He chases his ball etc. Thanks to your staff who I find to be most helpful my dog did not get vaccinated this yr. Instead I had a titer ran on him and he did not need shots. I would never known to do this if it weren't for you people. I told my vet about how often I express his glands and she said small dogs have problems with this and it is ok for me to do it for him. I worry I might hurt him but he doesn't show any signs of pain. I put meat, chicken or liver, in with the honest kitchen but I cook it first. I do not give them bones but I will try it. Is there any other source of fiber I can buy? He is a 20 lb. poodle mix. I give him mega daily pet tabs 1/2 a day I open the cap and mix it in his food--super C--garlic in the spring, summer, and fall for fleas, salmon oil and vita E, probiotics, and grand flex powder. He is such a cute, sweet dog I want to do all that is best for him. Thank You for your time and help, I appreciate it!

Patti