A smaller foam roller that you can take to the gym. You can pick one with the right density, depending on how comfortable you are with self-myofascial release.
Pro You can get options with different density
PhysioPhit offer pink, blue, and black versions of the roller with the first one being the softest and the last one being the hardest. Depending on how experienced you are with self-myofascial release and how much pressure you want to put on yourself, you can get the appropriate option and then upgrade if necessary.