Masters in Math degrees without requiring bachelor's in math
This is, typically, very difficult without taking courses in real analysis, numerical analysis, differential equations, and other applied mathematics topics that you won’t get in a traditional economics program.
Your chances would be, frankly, very low without proper preparation from mathematics undergraduate courses. I did an economic major with a math minor, and I am still upgrading a few courses here and there to go into an applied math PhD, but this would be similar to a masters degree because of the pre-requisites.
Take a year or two, get the background, and then you would be much more competitive. Perhaps you can illuminate what math courses, particularly, you’ve taken.