Hi! Welcome to the BYC! I am the chicken tender and coop cleaner at my place, and that is enough info to dissuade me from any sort of indoor chicken. Nope. Not even a visit. But, if you want to do that, I think diapers are the way to go. Seems like that will be a big mess too. Seems to me that you would have to give him a bath every time you change it. And if you don't change it often, your house will stink. I like the idea of getting a few hens and building a proper outdoor coop and run.
Well, I don't mean to be so negative. I know a lot of people do not feel the way I do about it, and they feel the benefits of that special chicken in the house outweighs the work it would entail. So good luck! I do hope it works out for you if you try it.
And just to show how big they get... This is Squatch with a normal sized barred rock hen. He is only 8 months old and he still has some growing to do. They don't stop growing until 2 years old. The first year they build their frame and the second year they start getting their mass.
So you'll want a coop he can get into. They're very tall.
YouTube has videos on making diapers out of socks and brassieres. One even has room for a disposable cup to catch the mess.
A prefabricate coop can be assembled inside the house, as can a dog crate with a baby play fence or puppy fence, then covered with a sheet to keep him in.