Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2279377.
Update 5/1 2017: Uploaded version 3 of the base. I increased the height of the base core to accommodate a large gap between the cover's rain lip and the base moat (for those with larger ants). I also refined the top cover once more to thicken the rain lip to print better.
Update 4/28 2017: Uploaded version 2 of the top cover. Some printers may not like printing the curved edge of the top cover (without supports), so I simplified the edge. Both versions remain available.
We are using beehive stands from BeeSmart Designs: http://beesmartdesigns.com/products/the-ultimate-hive-stand/
So I used RickS Beehive ant stopper ( http://www.thingiverse.com/thing:334608 ) as a frame of reference and re-created rectangular versions to match the legs of our hive stands.
I added a filling port and cap to make it easy to refill the moat with vegetable oil. So, no syringe needed.
This is available to edit on Tinkercad here: https://www.tinkercad.com/things/5K6Q2nsjON3-beehive-ant-trap-foot/
For our specific application, I chose not to use the cap. The hive stand fully covers the top. So, I drilled a hole through the base and top and used a screw to attach the ant trap to the bottom of each leg of the hive stand. The screw is in the cavity farthest from the filler hole. This serves two purposes, one to keep the hive stand from sliding off the feet, and two to allow the ant trap to be swung out from the leg to refill the moat with vegetable oil.