That's more expensive than when I looked into it for a project a few years back. Truth is you could piece this together with parts from other bikes but it's still kinda expensive, especially if you have to resort to aftermarket controllers. I think it was discussed on the forum to try the VanVan's system. I'd think an XT250 might be a decent donor as well but I could be wrong. Intake manifold and airbox boot sizes are likely all wrong but you could cobble something together there. The big hangup I'd imagine is supplying the necessary power to run the bike, just not sure if it would be up to the task or how to work around that. I'd think if you use a kickstart model you'd need something like the modern dirtbikes use to tell the EFI you're about to kick it over. Not to mention you're gonna need a fuel pump.
Honestly it'd be easier to pack an entire spare carburetor. Most practical is usually to just get familiar with the carb you're using and carry some jets and maybe a few other spare bits to combat clogs, leaks, and altitude changes. I know that's not the fun solution but it's the pragmatic approach for most peoples' situation. That said it would still be nice to have. Then you could have the carb as a backup in case it goes south and be prepared for anything.