Ok, now that so many people have responded I guess I'll give more info:
1. DS is crawling, so I can't put him on the bathroom floor because there are too many things he can bang his head on (he will crawl straight into things) like the pedestal sink, toilet, etc. so that's not an option.
2. He sleeps on our bed, and I can't really leave him for long enough to take a shower because if he wakes up, he starts crawling on the bed.
3. I could try bringing him in there with me, but I guess I would have to put him in his baby tub, and he would have to be cool with laying there the whole time. The bumbo is no good anymore, he arches his back and tries to get out of it, which is just too scary on tile. Maybe the rope tub thing would work.
4. I don't have an exersaucer. I could try the playpen...I guess I could just move it closer to the bathroom and leave the door open. My bathroom is SMALL so I can't fit anything in there like a swing.
I guess my biggest fear is not him crying, but him moving/falling/bumping his head, particularly in the bathroom because it's just hard surfaces everywhere! He's really super independent and active, so the idea of him sitting nicely does not apply!
I wish I had a tub! Then he would come in there and take a bath with me, but we only have a large shower.