it's simple: 1. trade in prius 2. buy plug-in prius there is another way, but it's for electric engineers with unlimited resources.
We have a couple recent threads on this. If you live in Colorado you can do this because you get $$$$ off from the State incentives. Here is price list: Upgrades | Boulder Hybrids
Also because a Prius owner who converted his Prius to a plug-in suffered a fire that destroyed his house, killed his cat, and, apparently, his insurance company fought his claim. No car, no house, no cat...
I'm still running a PHEV conversion that was transferred to 3 different vehicles through the years; beginning in 2009. Unfortunately, the the core electronics of the conversion I'm using is not longer available since a few years now. I had replaced and improved the power storage a few times also, and it had been reliable since the last 5 years with no glitches but expended a bunch of money to get to this point. Return on investment, not whatsoever but the happiness of the the accomplishment is unparalleled. It does take a lot of effort, patience and deep pockets as I mentioned before. It is a doable task with newest available equipment on the market .
Virtually a new car, dubious benefit, not a popular upgrade anymore, nixes the spare: don't do it, lol.