This model is a tasklight that I designed for my desk, but it should be adaptable for nearly any desk with a cable passthrough. 

It features connectors for ¾ ID PVC pipe paired with an adapter for a fluorescent tube protector

BOM

1 stick of ¾ ID PVC pipe 5ft ~$5

1 T8 fluorescent bulb tube protector ~$5

1 strip of LED lights 1m and as dense as you can find ~$5-10

3 M3x16

1 M3x 35

4 M3n

For the assembly, the most difficult part should be fitting the bulb protector into the printed adapter. It is a very tight fit. The files should allow for a little scaling as long as you scale the parts the same amount. I found that there is just barely enough room to slide a spare piece of the ¾ ID PVC in along with the led strip to squeeze the strip to the top side of the tube making use of the adhesive that is included with most LED strips. 

I'd recommend sanding and painting the PVC to give it a more attractive look and cutting the PVC to the final length you need even though with the clamp design, you could leave it a little long for adjusting the placement. I would also sand the bulb protector to diffuse the light a little better. 

For the pictured assembly, I used one 5ft section and one 2ft section which gave me the ability to position the light nearly anywhere over my desk. 

I am planning a version 2 that clamps to the desk instead of just slotting into the cable passthrough. 

If you need a stand alone version, I might recommend this model https://www.printables.com/model/617075-pvc-pipe-tripod-34-id to give it feet.

Additionally, it might be a good idea to leave off the end cap and trim the tube to fit the length of your LED strip so that heat doesn't build up and loosen the adhesive.