AtlasNerd,
A couple of suggestions...
One, can you get someone to come in during the day to let Bristol out to go potty?
Second, this is what I would do. I'd cover the whole room in newspaper. That way, he'll get used to the feel of newpaper under his feet when he potties. After a while, I'd gradually reduce the area that is covered in paper until you are just using a small amount of paper for him. It won't get rid of the daytime pottying, but it will make for easier/more tolerable cleanup.
PS. Many people make the assumption that you've made with regards to dogs being
able to hold it because they hold it at night. Unfortunately, it doesn't work that way. Their bladders "go to sleep" at night just like ours do which always them to hold it longer then. Don't you go longer at night without peeing than you do in the daytime?