Thickening Agents for baby formula

I was wondering what other thickening agents I can use in my 3 weekers formula? We were using Enfamil AR but the gas and constipation just isn’t worth it for us, I think it causes more issues with her reflux when she is backed up and uncomfortable.

I know rice cereal can cause constipation, and someone suggested we try oatmeal cereal. We are switching her back to Nutramigen, and want to thicken it to reduce spit up, but we don’t want to deal with the not pooping issues.

Any advice would be great!