I use one of 3 TP carriers;
Years (decades) ago I bought a screw top holder that is very compact and still works well (but is no longer made).
Since I use one of several vehicles I keep an emergency roll, and E-tool in each and have found that a large, (34+ ounce), square, Planters peanut jar works well once a roll has been used enough to fit (install fresh roll in the house then when it is used to the point where it fits; install a fresh new one and put the reduced roll in the peanut jar.
A year or two ago I got a port-a-pottie (Thetford). Since it is near certainty that something (vital) will be forgotten on nearly every trip I made a center dispensing holder out of a 2 liter soda bottle; once cut down its short enough to fit into the (clean) port-a-pottie with the lid down thus making sure that there will be a TP supply on hand, without the need to stop and run to the vehicle.. (The fall back plan is the traditional e-tool and the TP in a peanut jar.. always have a backup plan for the important things...).
Enjoy!