Any kitten specialists in Houston?

Mama cat left a crop of kittens on the front porch and my husband and I are doing our best not to kill them. They're roughly 4 weeks old, they got their first dose of dewormer yesterday, and we bottle feed them KMR with a kitto-friendly probiotic every 5 hours. At feed time, we stimulate their bottoms so they can pee and poop … only the damn sweet things won't poop. We've been handling them since Friday afternoon, it's now midnight Wednesday and still no s**t. I just finished up a feeding and introduced 1/4 tsp of pumpkin baby food into the mix, so we'll see what happens around 5AM, but I'd like to be able to call up a baby cat doc tomorrow and get some additional advice, maybe even an enema (for them, not us). I have spoken with The Cat Vet Clinic and while they were very helpful, they don't really deal with bottle baby kittens. If anyone has a lead on a vet that is super knowledgeable on kittens, we'd be much obliged.