Honestly, for inside the house, I use mostly adult sweatshirts, while they are baggy and hang down at the stomach, they are great for Kai to cuddle in to. (I was being even extra thrifty)
I did have a pair of Pj's made just for him (4 legged) but we only put this on at night when I will not have to let him out for at least 8 hours.
I would love to knit my own sweaters, but it is the leg part that I worry about the most.
If you want to see pictures, let me know...