I made some a few years ago for a multi club regatta. I based them on the USCG 5x11 Lighted Buoys; I have a copy of the some plans for USCG buoys in my stash of reference material. I ran the USCG Buoy Yard in NYC on Governors Island from 1989-93.
For the buoys I made here is a list of materials:
1 & 1/2" PVC pipe coupler
1 & 1/2" x 1/2" bushing for top end
1 & 1/2" pipe plug for the bottom
Eyebolt & nut
4" of 1/2" PVC pipe for upright
2" thick foam insulation, cut a donut - 5" OD, ID to fit coupler
3" diameter Styrene disk (2 for can buoy, 1 for nun buoy)
1 & 1/2" diameter Styrene disk (for nun buoy)
2" x 1" Styrene pieces for radar reflector (rectangular for can buoy, tapered for nun)
LED's with resistor (I used Miniatronics LEDs and resistors)
9V battery connectors and wire from Radio Shack
9V battery - fits neatly inside the 1 & 1/2" pipe plug and coupler
30 minute epoxy
The 1 & 1/2" x 1/2" pipe bushing is not glued to the pipe coupler; it has a nice friction fit that allows the battery to be changed.
I use duck decoy weights as anchors.