Of course, it goes without saying that you need your table, linens and lotions. Consider bringing more than one lotion in case your client has a preference for cream or oil. I prefer to use cream, but always brought my nut free oil when doing an outcall for the first time in case of nut allergies or a preference to oil.
I never do a massage without bolstering, so a bolster would be a must for me. I would highly recommend bringing it for your client's comfort or for special situations that would require it.
When you bring your linens, don't forget a light blanket of some sort in case the client is chilly.
I would also add to the list music. When doing outcalls in a home, you can ask if there is a CD player in the room where you will be doing the massage, so you might not have to cart the player. Although, I always brought my own because I knew how to operate it and it saved some time for me.
I don't use a stool so that was never a consideration for me, but if you can do massage without it, then it would save you some carting. If you do bring it, I would get one of those portable folding ones.
Don't forget to bring paperwork. Your business cards and brochures, as well as intake forms, etc.
I always would bring hand sanitizer as well. Of course, I would always ask to use their restroom to wash my hands before and after the massage, but using the hand sanitizer, especially after the massage would save me from putting greasy hands on their doorknobs.
You might also consider something to tell time too. Some people have those watches that hang from a belt loop. Since I can't see those, I would always bring a portable alarm in case the room we were in didn't have a clock that i could see.
Boy, it sounds like a LOT to carry around. That's one of the many reasons I don't do outcalls anymore. It takes a certain personality and I realized that I just didn't have it.
Best of luck to you.