Not an easy one.
Some of the newer Infinity models may be compatible. They'll be smaller that the Prodos minis, but at least with the same proportions, which is the main issue regarding scale issues. The difference in height would reflect that of real people, specially since military guys have a taller average height.
But civilian minis, unless I'm mistaken, only appear in some sets (Dire Foes misión packs), so unless you can find them loose on eBay you'd have to pay for the whole set to get one mini.
Tom Mason, with his Effigy Miniatures company, released a couple of civilians, similar in build and very tall (36-38 mm to top of head, more or less). OOP and quite rare to find.
Warzone Resurrection, being by Prodos, are 100% compatible scale-wise; but off the top of my head I don't remember any civilian mini, not even one that could be easily converted.
RAFM has a mini in their USX Modern Heroes of a librarian that I think is quite tall, about 35mm. No idea where I got that info from, though. And he's not very sci-fi looking.
There's also the OOP Governance of Technology civilians, from Antenocitis Workshop. Again, this range had quite tall minis, so I guess the civilians wouldn't look out of place next to AvP marines. If you can find them, that is...
That's about all the help I can provide.