hi mate your in a bit of a pickle here, resistance is a game upgrade which takes flashpoint to version 1.75 and then patches can be used to get to version 1.96. To get a copy of resistance you need to buy it from either Codemasters or track down a copy on Ebay, or look in computer game shops but i think that it will be nigh impossible to track it down. If you go to the official forum (google BIS flashpoint forum) and ask there as that is the best place for the answer your after.
GI-YO