Hi, my name is Stefan. I'm an experienced audio engineer, working in my own company with a team of two co-workers.
I'm not sure if you mean the right thing: so obviously you have mono files, do you just need them to be stereo files? It would still be mono source, in a stereo container if you want to name it like that. If you want to hear some sounds left and some right (panorama) it would have been essential to record it in stereo. I (and anyone else) could just add a kind of "fake" stereo, but it won't be the original stereo image. If you copy the mono track, pan one left and one right, it's still mono, as there's no stereo information in the recording. Let me know what exactly you need. Turn around time is 1h