Lockbox in car?

[GoDirectly2Jail]

Your question is not likely to get other than basic, generic answers because it is not firmly grounded in the hypothetical. In fact, it would be exactly the sort of thing that people who wish to skirt the law would want to know.

If you can provide a satisfactory explanation on why you would need this type of information, the quality of response would likely improve.

[BP348]

What do you mean, exactly, "an alert allows...to be searched?"

If the driver were to refuse to open the box (let's assume it's more like a mini-safe than a cash box - unbreakable), and informed the officer he would gladly comply if given a warrant, would they be within their rights to do so?
What actions would follow?

.....you know how to PM...

A K9 alert is PC to search so if the K9 alerts to the safe and the driver refueses to open it then you call the locksmith or whomever else you can think of who could open the safe. One way or another the safe is going to be opened.

Also just FYI a locked cashbox really isn't that big of a deal.

I really don't think anyone here is going to give that type of information to you either out here in the public forum or by PM.