The free .fga vector fields work fine with PopcornFX

Be advised the scale of the vector fields in this pack should be around .01 or so. If your vector field appears odd, try tweaking the overall scale and magnitude of the fields. The orientation of the vector fields may also need to be adjusted, -90 on the x axis should do it. 

PKFX has a very nice vector field visualizer, but some fiddling around is probably going to be needed since each one of these vector fields was built for other purposes and on a different platform.

Once you get dialed in, however, these .fga vector fields are great.