Option 1: Switch to a 4watt CB
Option 2:
Aron, what kind of vehicle do you drive?
Vertical separation may help, but that applies much more to a tower than a car, however the roof of a truck vs off the bed or hood may breakup the path so the antenna isn't taking a direct hit. There's one scanner for me that sees primarily 800mhz use for me, with it's expense if you're in that boat, maybe consider keeping to a duck antenna in the car and using the metal roof for separation (a rain cap for the mount on the roof may be cheaper than a new scanner).
You also need to take a look at the whole system; make sure that if the coax for one antenna goes up to the roof on the right, but the coax for the other antenna on the left, or go with expensive highly shielded coax (or do both). If they're run up together and not really well shielded, you may well be bleeding one into the other long before it gets to the antenna. But the more leaky RG-58 is also much easier to bend and route through cars tight spaces and odd shapes.
And also though, probably less so, consider placement of the radios in the vehicle; if the CB shop opened one of the radios up and cranked the power on it, their may be less or improperly restored shielding and that shielding may be too weak when the RF inside the box is beyond design limits. Not familiar with the amps you're looking at, but I can usually spot the guys running amps on the highway as I get a burst of static on the highway around their cab, even if they aren't talking (but take a look and you find the big antennas with the coil, and sometimes hear them come on and play their roger beeps on 19 for all to hear). Due to their illegal status some of the amp manufacturers put out crap products that cause such issues for others (not saying all cause I know some of it runs very clean, but it's something to be aware of, wrong choice and you may fry your scanner in much less time). And I want to be clear I'm not flaming, and think that if there was a 25-50 watt limit on CB, many of the shenanigans would be avoided and the playing field would be quite level; but there are a few more factors you may need to look into ruling out.
CB for me is more ears than mic so on my last car the CB was about 3 ft from my ham antenna and 5 foot from my scanner antenna, the cheap 4w CB didn't bother the other two, I could watch the RX signal needle jump on the CB when keying the 50 watt ham radio, never did fry it, but stopping by the next walmart or truck stop and throw in a $35 cobra or uniden wasn't a big deal to replace it for the mostly listening use. Just changed vehicles earlier this month, initially at least, I'm looking like it will be a minimum 6ft separation for just about everything, at least until I find an excuse to cultivate an antenna farm.
I know a lot of the commercial installers I've met use 1/4 wave separation as the absolute minimum rule of thumb, and that's usually with far more selective radios designed for commercial and public safety use, and generally in the 50 watt range. If it were a 4 watt CB, that would be so little power that it shouldn't be as much an issue. There can be some trial and error to eliminate the mixing, a few mag mounts and moving things around until the desired separation is there, then drilling holes is something to tuck away in your mind when it comes to the next vehicle.