i think is not a DIY procedure, studs are integrated to the hub by applying pressure and i dont think studs are sold in retail. i have one stud broken on my left front wheel, i was concerned at first, but then see there is no problem running with only three bolts. im expecting change all the hub like i did for my rears.
but if you want to try, first you need to find a specific stud and the uninstall the wheel hub, (is far more complicated on the front than the rear ones), and then send to a workshop for the installation. and after that im not sure if the fix will work for long (if it works)
NOTE: Old car models used to work with this fix, so you will find lots of people given you the repair advice.