Here's a reverse protection circuit using an N-MOSFET and a comparator to act as an ideal diode and block reverse current through Vcc.
It's ON voltage drop is just the output current times the MOSFET ON resistance
I put the MOSFET in the negative leg so a cheaper N-MOSFET and a common LM 339/393 comparator that can work on ground based voltages can be used. (That comparator input can't work at the high side voltage.)
The comparator monitors the voltage at the MOSFET drain and when the drain voltage is negative, indicating normal current direction through Vcc, the comparator output is positive, turning on the MOSFET.
If the voltage goes positive, indicating the current is reversing through Vcc, the comparator output goes low, shutting off the MOSFET to prevent reverse current through Vcc.
Note that the normal current flow for this circuit is through the N-MOSFET from source to drain.
This works because MOSFETs conduct equally well in either direction when ON.
D1 is for simulation purposes, to prevent reverse current through Vcc1 when the Vcc1 voltage is lower than Vcc's.
Note that, for 5V operation, the MOSFET must be a logic level type where the Rds(on) is rated for a Vgs of 5V or less.
The LTspice simulation shows the comparator output voltage and the VCC current going to zero when Vcc1 (plus the diode drop) exceeds Vcc.