Found this, and seemingly it could work on the ipad with an ATT and Verizon sim.....
http://www.redmondpie.com/dual-sim-card-adaptor-for-iphone-4/
only thing is you would need to tape it or something to the back of the device....
http://www.redmondpie.com/dual-sim-card-adaptor-for-iphone-4/
only thing is you would need to tape it or something to the back of the device....