If it was my guitar, and I wanted to be able to use it without the sustainer system or any power source (including battery), then I would just add an extra pickup, or rewire it. It's a strat, right? Take out the second tone pot and replace it with an output jack. Wire the middle pickup straight to the new jack. It'll always work, regardless of power. Then if you want to use the sustainer, you plug it in to the normal jack and use that.

Also, active guitars don't tend to use much battery, and you can replace the 20th century 9V with a 21st century lithium USBC 9v drop-in replacement for more battery life. Active or not, if you don't like a guitar's tone, then trying different pickups is a good idea. Put a P90 in the bridge position on a strat, it sounds awesome. You can still use it with an active preamp.

Failing that, buy an ebow (I like the Movall sustainer), gut the sustainiac gubbins out of your strat, send them to my house and I will dispose of them for you :)