No reason to believe it isn't a JIS square taper interface. A bike shop should be able to get you a new replacement for around $30-35. At this price range chainrings aren't interchangeable, and with more expensive MTB cranks your big ring will be 42 or 44 teeth. The other option is a road crankset, which will lead to a new front derailleur (more $) and shifter (even more $). Pedal faster or see if the shop can set you up with a smaller cassette or freewheel. They can look at your hub and tell you what the options are.