Brett, you might be able to rig up something simple that you could dump a bag of cheap feed/grain into when you visit. You would need about a 40 degree exit ramp, shade, a lid and some small vents. If you can make the ramp lead to a pipe you could extend the pipe out over your pond and the larvae will drop into it.
Honestly it would be hit and miss and it would be tough to get a significant amount of larvae.
