Basic build is a s follows. I took 1 1/4" to 1/2" reducing coupling and slightly cut them down. I then used my Dremal to wallowed out the inside of 1/2" PVC pipe to allow for the light build to slip in. I then added grooves to either side to allow room for the wire to pass either side.
The 1 1/4" to 1/2" reducer had an outside diameter of 1 1/2" which allowed me to buy 1 1/2" inside diameter acrylic tube for the outside of the light. I sanded it down with sand paper inside and out to diffuse the LED light. The acrylic tube is attached to the PVC pipe using small stainless steel screws so I can remove it and access the bulbs if I need to.
My own twist was I added a second LED to act as a strobe, so a dual LED light setup. It took awhile but I found the right strobe controller which gave me about 300 pulses per minute. I wanted to added the strobe feature for crossing waters in high traffic areas such as the Aransas Shrimp Channel or paddling across Estes Flats. I used a DPDT toggle switch to let me choose either just the constant burning bulb or the constant burning bulb with the strobing bulb.
The power supply is a 5V/2A 5000mAh power bank ran through a 5V to 12V step up converter. Both LED's with strobe controller pull about 700mAh (the single constant LED is about 300mAh), and I'm not smart enough to do the math on the power loss from the 5V to 12 V converter. I'll report back after this weekend to see what kind of battery life I get.
This all fits in a 12" long 1 1/2" PVC pipe, and then I used a reducer to glue in my 1/2" PVC light pole. Because the switch was so wide I used my heat gun to flatten out the PVC tube so the waterproof switch could sit flat and be sealed.
Here's a schematic of everything without the wires connecting everything.
I finished the tops around the acrylic light tube with rubber caps. Here's the finished product with paint.
A video with both bulbs on from about 40 yards: https://youtu.be/pdro0qHbBLA
I made two of these and they each came out to about $50-$55 per light. I made most of my purchases on Amazon: LED Bulbs, 5V Power Bank, 5V to 12V converter, Pulse Controller, Switch, 2' of Acrylic Tube, and Rubber Caps.