I have seen chicken diapers and saddles(for hens) advertised on BYC now and then. If you google chicken diapers I'm sure some will show up. I don't think the smallest baby diapers would work on chicken. Even a 5 lb. baby is alot bigger than a chick. My friends has had house chickens for many years and never used diapers - but she should. She is cleaning up endlessly after them. I would think a small batam breed like Seramas would be easier to make into pets - that is what they were developed as.
I think they still need outside time to scratch and hunt and do chicken stuff, they aren't puppies. My friends seems to overlook that. She wants to be the center of their universe and as people often point out chickens prefer to be with chickens. She has birds(canaries, finches etc.) beta fish, turtle , dog etc. I wish she'd just let chickens be chickens and not expect love and loyalty like dog.But I can understand having small chickens as housepets just not as dog substitutes.