The problem you have to solve is that the upper two NFets will be operated as "Source-followers", meaning that to fully turn them ON, their gates must be pulled to a voltage which is 10V or more positive with respect to their sources, which because they are saturated and have only a tiny voltage from source to drain is effectively 10V or more positive than the V+ in the posted schematic. You will have to construct another power supply, and rewire the op-amp drivers so that they can produce the required gate voltage. Note that the opamps driving the upper NFETs must also be reconfigured to invert the gate signal compared to the way they are configured now.
A lot of work to avoid buying two PFets.