Yes, you would have to mount the parts from a stem shifter onto the Origin 8 clamp, but it may not be configured correctly to allow you to mount the hardware for a stem shifter on to it. Very difficult to determine without inspecting and measuring everything involved.

But do you really need stem shifters? They are the worst possible option, being something invented (along with suicide levers) for people who bought "10 speeds" during the initial bike boom of the 70's and who then wanted to just ride on the top of the bars. They take your hands well away from the brakes when shifting (suicide levers are not real brakes) exert a turning force when you shift, and many work poorly. What is your reason for wanting to mount stem shifters?