Use your handheld radio, or go to another airport that's lighted, or call or text someone on your cell phone, or keep flying till (full) moonrise or dawn, or fly to the handy nearby desert dry lakebed where space is unlimited and the white surface will visible to dark-adapted eyes even by starlight. In the latter case, to compensate for lack of depth perception, you may need to use the procedure used by floatplanes landing on glassy water-- maintain a constant, low descent rate till the wheels touch.
Or do a low-altitude buzz job on a nearby neighborhood, all-night gas station, etc-- maybe you'll get someone's attention. (But try buzzing the airport first-- if anyone's there, they should soon realize what is going on.)
Apparently flying in triangles used to be a distress signal to ATC, but has now been abandoned (link to "Quora" answer).