This hand control is manufactured by Tranquil Ease, and is sometimes used with Chairs that have an Okin or equivalent system.  The back of the control may list a “model # 2802HL-PR3” on the control. It has a one piece cord with a nine pin screw on connector that looks like what would screw into the back of a computer.

Some versions of this control have a round 6 pin quick disconnect connector, and the extension cable on the quick disconnect then goes to the control box under the chair. Those quick disconnect models are not made any longer, so if you have one on these, just eliminate the quick disconnect cable, and run the new hand control plug all the way through the chair and down to the control box under the chair.