I had the same issue for the 225W box mod and here is the solution...
So I had this problem too after repeatedly dropping my Smok Mag. 3 of 4 screws were removed, and the batteries would not stay in contact to fire the device. I used some electrical tape to secure the 'mag' at first knowing that was a temporary fix. From what I have found, there is no information or parts available anywhere to fix this issue.
After researching and some measurements, I found the screws are M2 .4 x 5mm. I was able to finally locate some M2 screws at a local Home Depot, however, they were only available in 6mm and 8mm lengths. I bought both, and just seated the base using the 8mm version. I thought this might be better since the 5mm screws were stripped and wouldn't even grab thread.
Hopefully this helps someone out there as it's been somewhat annoying trying to track this down and make this work. Note, the replacement M2's are flat head Phillips rather than Torx T5, but imho it doesn't really matter so long as you don't strip them.