USB interface

I want a USB cable that interfaces with an opto-coupler. The function is to count speed pulses from a 24 volt truck computer (up to 5kHz a second, which is the input to the opto-coupler) and provide an isolated 5 volt output which is to be totally isolated from the input. The opto-coupler MUST have a VERY HIGH input impedance otherwise it will cause a loading effect on the truck computer. So USB plug, 400mm of cable, then opto-coupler interface, the another 1200mm of cable (to the truck computer). The opto-coupler must be professionally housed in-line with the USB cable. Initially I want 5 for testing purposes then purchase by the hundred.