For someone who may be reading this thread later, we make exterior cedar gates that have pet openings, as opposed to pet doors. Check your local code requirements if a pool is present, as communities have height limits that need to be met. We do not recommend having a dog door or pet opening if you have infants around, as it is a safety risk.
Custom Deck Gates with Pet Door Opening
You can see the actual opening (you spec the size) on the Gallery page. You can get them pre-built or as a kit, which an save you some money on shipping costs.