What pressure does liquid nitrous oxide need at −45 °C?
Using NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) – NIST Standard Reference Database 23, Version 9, I found the saturation point of nitrous oxide at equilibrium for a temperature of $T=-45.000\ \mathrm{^\circ C}$ at a pressure of $p=783110\ \mathrm{Pa}=7.8311\ \mathrm{bar}$;
for $T=-78.000\ \mathrm{^\circ C}$, it is $p=182290\ \mathrm{Pa}=1.8229\ \mathrm{bar}$.