You shouldn't heat the whole bottle.
- You risk to evaporate more than you want
- You would need to adjust the heating power to the gas consumption
The better and usual method is to harvest liquid nitrogen from the bottle and heat it after it has leaved it.
That is, by scooping the liquid, pressure changes little in the bottle. Heat leaks through the bottle to the liquid must suffice to produce the volume of gas replacing the mean stream of liquid, and the volume and pressure of the vapour in the bottle averages the short-term demands.
Once the liquid exits the bottle, you evaporate it, and usually bring it near room temperature, by a heat exchanger with the atmosphere that eliminates the adjustment. This exchanger must work when ice-covered as well.
As the bottle must leak a bit more heat than needed, pressure increases too fast, so you add an overpressure valve releasing vapour, hence from the top of the bottle.