A quick Google turns up this kind of thing [0] which, based on the price point and form factor, is aimed at tow truck operators rather than individual drivers. Costs $10k+ and will take up most of the back of your car.
That's a commercial unit again, not something you throw in your trunk.
That's probably the right solution to this - and something every tow truck will carry in 10 years - but it's not the "capacitor in the back" analogue to an empty jerrycan.
https://mobileevcharging.com.au/