3Way Occupancy Sensor Switch NO neutral or grounding!
It's going to be a little tough, mainly in the search for appropriate products.  Stack Exchange is not a shopping-assistance site. 

A motion-sensor switch needs energy to function.  The old way was to place the switch in series with the bulb, which depended absolutely on an incandescent bulb - that won't work in your case.  The other way is to power it conventionally by bringing always-hot and neutral to the switch.   You need this method. 

First, you already have 3 wires between the power supply/lamp and each switch.  Redesignate them as follows: 


Actual Neutral (must be white or gray)
Always-hot
Switched-hot (which controls the lamp) 


Then search for a matched set of smart switches (which are made to work together) which do what you want, and are compatible with that wiring.  

For instance, two modern motion sensors (which take hot and neutral) may be able to work, each of them switching the switched-hot line.  

Often, they are engineered products where one is a "master" and the other is a "remote".  Either you need the type which communicates wirelessly, in which case switched-hot is only used by the master.  Or, you need a "controller" up at the lamp, with two "remotes" at the switch locations, in which case the "switched-hot" is used for a communication wire instead. 



To add to this answer...  if you are obliged to rewire, then given the low overall power requirement of the lamps, I would consider doing all this in low-voltage lighting.  The wiring is a lot easier to work with.