The only splitter in our shop that would work is
splitty9. You can connect the PWM signal of both pumps to one fan channel but it is questionable if you will be able to control the pumps because most PWM enabled D5 pumps use an incomplete PWM implementation which is missing a pull-up circuit for the PWM signal. In such a case it is possible to modify the pump to be compatible. A tutorial can be found
here for example.