I've seen American sites refer to Future Floor Polish but I haven't found any in WA. I use Tamiya's flat clear spray for my work.
I don't know if it adds protection but it 'levels out' the differing shininess of the paints used and generally makes them look nicer. Plus it can take some of the stickiness away.
I get mine from hobby shops. I have seen Bunnings stock gloss and semi-gloss clear sprays but haven't tried them.

Hope that helps.