I use an Elecom Relacon, a trackball in the form factor that you grip like half of a gamepad, or maybe a Wiimote, but it's Bluetooth with no gyro. LMB and RMB a

I use an Elecom Relacon, a trackball in the form factor that you grip like half of a gamepad, or maybe a Wiimote, but it's Bluetooth with no gyro. LMB and RMB are the shoulder bumper buttons, scroll wheel is near the ball flanked by forward/backward buttons. Typically about $50 on Amazon, runs on two AAA batteries.