The remote control is the Philips IR remote RC5 or RC6 protocol. A simple universal remote control will work fine. E2V Argus helpfully decided to use a standard protocol and buttons. They even used relabelled universal remote controls themselves. A good cost saving for production. The One for All series product code is 11233.
On an Argus 4 the following buttons apply. Check the manual for further details.
Power is the Menu activation
Ch up is Menu up
Ch down is Menu down
Vol down is -
Vol up is +
Mute is OK and Delete
Fraser