USB Remote control switches come in all shapes and sizes. The most useful, I have found are single foot controlled switch (FS1-P) and triple foot controlled switch (FS3-P). Using a digital book player with foot switches allows persons with severe motor control troubles symptomatic with MS, ALS, cerebral palsy, and, persons without hands or working fingers, to read talking books. Player is operated by programming the Play/Stop button to be activated by foot switch. Leaving the player powered on and plugged in, persons can start and stop reading activities with single switch. Triple switch allows DA1 navigation and play by programming menu, previous and next buttons. Holding menu key down also allows bookshelf feature activization. Play/Stop button may be substituted for programming menu key if desired. This limits navigation to first DAISY level. Both  foot switches are commercially available from China on Amazon. Prices range widely. Fair price for the single switch is 7-12 USD. Fair price for triple switch is 17-30 USD. Search terms are FS1-P, FS1_P, FS3-P, FS3_P, USB foot switch, etc. Xbox controls work well though joystick features on xbox can't be programmed. Xbox controls with dongle can be used as Bluetooth device. Some Joystick controls with flight control hardware are usefil in certain circumstances. Atari styled joysticks, from experience, do not seem to work. Remote USB Num pads can control all buttons of the players except power button. Recessed power button can be adapted using 5/8 inch bump dot.  Not all USB devices work with player. Gaming devices are most successful.