[resolutebat]

Yes, they do, and it's available as a service in Australia:

https://mobileevcharging.com.au/

[dmurray]

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.