I've gotten board/curious and used my premium hair clippers to try to shave my mustache a few times. Using a 000 (0.5mm?) blade, it doesn't cut anything - mustache too short but not stubble-length short. You'd probably need a 0000 (0.25mm) or 00000 (0.20mm) blade to get stubble length using clippers. For that, you'd need interchangeable metal blades. A 0000 and lower blade usually doesn't come with cheap clippers.
Get an Oster Fast Feed for $60 off Amazon and a 0000 or 00000 blade. Probably about $20 for the blade online. Watch out for razor burn because you're dry-cutting.
Otherwise, there are some cheap Philips "beard groomers" I've never tried.