Here is a list of the parts you will need.  They can be found at either Home Depot or Lowes, and the D-Rings come from Wal-Mart in the crafts section mixed in with the replacement buttons.  You will only need one of each item, so the extras in the bags will give you plenty of room for error, or practice!

#1) M4-7 Class 8 Hex Nuts
#2) M4-7 X 20mm Class 8.8 Hex Cap Bolts
#3) M4 Wave Lok washers ( curved washers )
#4) 3/8 X .171 X 1/2 Nylon Spacers
#5) 1/2 X .375 X 5/8 Nylon Spacers
 
 

At ACE Hardware, per Quartz:

Nylon Spacer- OD: 1/2" ID: .375" Length: 5/8" ($0.25/ea)
Nylon Spacer- OD: 3/8" ID: .171" Length: 1/2" ($0.16/ea)
Hex Cap Head Bolt: M4 x .70 20mm ($0.23/ea)
Hex Nut: M4 x .70 ($0.05)
Locking Wave Washer: 4mm ($0.06/ea)
 

Next we're going to give the large spacer a slight curve to the bottom so it will fit flush with your saber tube. 

Wrap a 1-1/2" dia tube with sandpaper. 

Mark 12:00 and 6:00 on top of the spacer, I used a red sharpie marker! 
This will give you correct orientation for sanding direction. 

Sand the bottom of the spacer across your sandpaper tube in line with the two dots until it fits your sabers contour. 

See photo for reference.                        
 

Mark 3:00 and 9:00 on top of the spacer. 

Follow these lines down the sides of the tube and mark a line 5/16" up from the bottom, and 1/8" wide on each side. 

The lines should have rounded ends.

Cut slots along the lines you just drew at 3:00 & 9:00 making sure you leave the ends of the slots round. 

This is where a small round file comes in handy. You should be able to fit the D-Ring into these slots without any trouble. 

Here's what it should look like when you are done:

Insert the smaller Nylon Spacer into the larger one. 

Place the assembly on your saber tube to give the two spacers the correct alignment.  You'll notice that although both tubes started out 1/2" long, since you curved the bottom of the larger one, when you place the two together on the saber the inner tube sticks out of the top a little. 

THIS IS GOOD! 

Mark dots on the inner spacer 4mm. up from the bottom in the middle of each slot. 

Remove smaller spacer, and drill out the dots with a 1/8" bit.  It helps to use a smaller bit to make pilot holes first. 

See photo for reference. 

Cut a slot in the middle of the D-Ring 1/8" wide, or just wide enough for the main Hex Bolt to pass through. Attatching the D-Ring to the assembly is the last step, but you will have to first pull the ring appart just far enough to clear the width of the inner Nylon Spacer, or 3/8" wide.

Glue the small spacer into the larger one making sure to make the smaller one stick up out of the large one slightly like it rests on the saber tube.
 

You'll want to paint the assembly next, but here's directions on how to attach it all to the saber:
 

Insert the Hex bolt down through the assembly 

You may have to drill out the space between the tabs of your saber (Graflex Bulb holder tabs) just enough for the bolt to go through. 

Place a Wave Lok washer (curved washer ) onto the bolt from the bottom, then a Hex nut. The washer should fit the contour of the saber tube. 

You may also want to grind the bolts end down a little so it fits flush with the Hex Nut.

I have included a couple of refernce photos for painting purposes. 
  
I really have no idea where I got these, But I know it was probably another board member so I appologize for not giving credit for them. 

If anyone recognizes them as their own, and does not wish them used here, I will remove them. 

                          ------------------------------------------------------------ 

Here are a couple of views of the real saber at the MOM tour. You can clearly see that the inner tube is RED! There is also a small red dot on the front of the assembly offset. 

Prime the assembly first, then spray with a flat black Epoxy based paint. 

If you wish to replicate the Red insert, this can be done by hand before attaching it to the saber. 
 
 

And that's all there is to it.