Aydan, may I ask why it is impossible for you to do face-to-face meetings? I would think it might be easier to have a sponsor based on a face-to-face meeting, easier to work the steps in person than online, but if you have no other options, I guess I don't see why you can't have an online sponsor...
I don't know how to go about finding a sponsor with specifically a military background other than maybe attending some face-to-face meetings held near military bases or perhaps in VFW posts or the like, hoping that there would be a higher percentage of folks w/a military background in a setting like that. Maybe you can contact the Alanon central office for your region and see if they can advise you at all.
There is a lot of experience on this forum and hopefully someone else will have some better info for you than I did....