There are no docking stations, cheap or otherwise, that would let a 5th-generation iPad with a Lightning port drive a Thunderbolt Display. Even Thunderbolt 1 is a much more capable interface than Lightning. Much greater speed, designed with resolutions of >1080p in mind, and designed with external PCIe-style expansion in mind.
One could imagine building a special-purpose computer with both Lightning and Thunderbolt interfaces that could act as a bridge, but it couldn't do anything to increase the severely-constrained bandwidth of your Lightning port. Such a device might cost hundreds of dollars, and would not be able to let you take advantage of the Thunderbolt Display's 2560x1440 resolution, or to attach other types of Thunderbolt devices that your iPad simply has no idea of how to support. It would be a Frankenstein's nightmare kludge that cost a lot, and had very little to show for it – other than the proof of concept that "The monster lives!"
There would be no market for such a device and it would be an instant money-loser. Nobody is going to build one. As much as you want to use your Thunderbolt Display for your iPad, I don't think it is ever going to happen.
