Encoding Video For Archiving Using Premiere Pro CS6
The thing is, whatever you do you will still have to re-render your files, they have to be re-encoded. Some small amount of quality degradation/compression, however miniscule, is inevitable. My best advice would simply be to try and match you sequence and render settings as close to the original files as possible, find a file size–quality ratio you feel comfortable with and just go with that.

To give a more practical answer for you specifically: I'd choose "Quicktime" under "Format", "MPEG-4 Video" under "Video" > "Video Codec", click "Match Source" and also drag the "Quality" slider to a 100%. Don't forget to uncheck "Limit data rate..." under "Bitrate settings". Audio settings should be pretty straight-forward.

Remember, these settings are mostly a guess based on the information you've given and some tests I ran on my Mac using Premiere Pro CC 2014 with the codecs I have installed on it. Hopefully someone with more knowledge of codecs/video encoding will pop in and give a more fleshed out answer eventually; but for now I think this is your best bet.