Tesla confirms it's working on an aftermarket Model 3 Performance Upgrade package
If you didn't think to check the option box for the $5,000 Performance Upgrade package when ordering your Model 3 Performance, Tesla is working on a solution for you.

Tesla confirmed via Twitter today that it was working on offering Model 3 Performance owners the option to buy an aftermarket Performance Upgrade package that would include Track Mode for those who didn't tick that option box during the order process.
We’re working to provide an aftermarket Performance Upgrade Package when Track Mode becomes available
— Tesla (@Tesla) August 31, 2018
This is likely in response to a number of owners voicing their dissatisfaction that the Tesla Model 3 Performance's decidedly awesome but as yet not officially rolled out Track mode wouldn't be available on cars that don't have the additional $5,000 Performance Upgrade package.
The Model 3 Performance with the Performance Upgrade package is a seriously fast and fun car.
To be fair, when orders were opened for the Model 3 Performance, Tesla didn't expressly make clear that this not-especially-cheap option package would be required to get the full measure of fun out of the Model 3 Performance, so if I'd been one of the people who shelled out $65,000 or more, I'd have probably been pretty upset too. But, that's not the whole story.
The Performance Upgrade package consists of a few things in addition to an enabled Track mode. Specifically, the uprated brakes, suspension and tires. These things are pretty critical on a car with the capabilities of the Model 3 Performance, and enabling a Track mode that allows more movement from a car without them would border on irresponsible.
Arguably, the Performance Upgrade package's biggest change is to the Model 3's previously only adequate brakes.
It's still unclear at this time what an aftermarket package would look like and how it would compare with the $5,000 cost of ordering it with your vehicle, but it may prove to be popular with second or third owners down the line.