I made my own because one did not exist. I wrote it up quickly, so it might not be fully optimized, but it's reliable and it works just fine. Instead of calling a service to receive the assembled cloud, this publishes the assembled cloud on every callback. For this reason, it's less efficient than ROS's laser_assembler, but it serves my purpose just fine. It also provides a service that allows you to pause the assembler so that you can view a cloud without it being updated. You can find the code here.