Want to replace push-button with IR receiver
Information given: IR receiver PT333-3B phototransistor, Transmitting circuit is IR diode with constant dc current when turned on, and desire to use latching circuit via IR receiver instead of pushbutton switch.
Based on the information and given the circuit that you want modified there is a way to  adapt the circuit to your needs. Unfortunately, because the switch 1 in your circuit is connected between two nodes that aren't typical for use with a simple transistor. However a signal relay is appropriate since a relay is simply a controlled switch. The G5V-1-DC12 relay is an example of one relay that can be used since it's for low power signaling. In addition to signal relay is the circuit to trigger turn on the relay from phototransistor. Here a phototransistor will turn on the PNP transistor and thus turn on the relay.