rkruz

I purchased replacement LEDs from Ebay from a company called LighthouseLEDs.com.  20ea for $9 including shipping so about $0.45 each.
  I have already removed that bad LEDs and soldered the in these replacements and the brightness and light color are indistinguishable from the originals.   The entire bank of 3 that were out are now working once the bad LED was replaced.
The part number and seller info is in the attached photograph.

After a short search, Ive not found a specific LED replacement but made some discoveries that helps to narrow down the search and I am still looking for a LED replacement.  In general the square LEDs appear to be in the $0.50 to $2.50 each.
The LED board is very easy to remove. Loose 1 screw and slide the board out.
A 3 position toggle on the board selects White, UV or OFF.  There are no active components on the board, only LEDs, resistors and a toggle switch.  The simplicity of the board again makes for a very easy low risk LED replacement.
The white LEDs are connected in banks of 3.  If one LED fails the entire bank fails.  See the attached picture showing the white LED.  In my case I have 4 LEDs failed hence a total of 12 LEDs not lit.  With a DVM set in "Diode" mode, I can actually turn on individual LEDs installed on the board and have identified a single LED in each back that has failed.
The LEDs themselves have no identification markings on them to help find a replacement.
The white LEDs appear to be the style of 7.62mm square, using through hole wires and runs from 3VDC. 
The through hole wires  along with the large solder pads make it a very easy LED replacement for someone mildly experienced using a soldering iron and solder wick or solder sucker.  See the attached picture showing the leaded LEDs on the board.
THE UV LEDs are a different style but none of these have failed.  See the attached picture showing the UV bank of LEDs on.
The board is marked with "APQS" so they should have the circuit card design to include the mfr and part numbers for the LEDs should they care to share that information.
If I can obtain LED replacements I will create a "How To" video detailing how to replace the LEDs.
As for my background I have 2 Masters Degrees in Electronics Engineering and 40 years of experience designing electronics and managing the development of high technology systems.  Much my experience was performing detailed electronic design, which this board would be of the simplest example.

After a short search, Ive not found a specific LED replacement but made some discoveries that helps to narrow down the search and I am still looking for a LED replacement.  In general the square LEDs appear to be in the $0.50 to $2.50 each.
The LED board is very easy to remove. Loose 1 screw and slide the board out.
A 3 position toggle on the board selects White, UV or OFF.  There are no active components on the board, only LEDs, resistors and a toggle switch.  The simplicity of the board again makes for a very easy low risk LED replacement.
The white LEDs are connected in banks of 3.  If one LED fails the entire bank fails.  See the attached picture showing the white LED.  In my case I have 4 LEDs failed hence a total of 12 LEDs not lit.  With a DVM set in "Diode" mode, I can actually turn on individual LEDs installed on the board and have identified a single LED in each back that has failed.
The LEDs themselves have no identification markings on them to help find a replacement.
The white LEDs appear to be the style of 7.62mm square, using through hole wires and runs from 3VDC. 
The through hole wires  along with the large solder pads make it a very easy LED replacement for someone mildly experienced using a soldering iron and solder wick or solder sucker.  See the attached picture showing the leaded LEDs on the board.
THE UV LEDs are a different style but none of these have failed.  See the attached picture showing the UV bank of LEDs on.
The board is marked with "APQS" so they should have the circuit card design to include the mfr and part numbers for the LEDs should they care to share that information.
If I can obtain LED replacements I will create a "How To" video detailing how to replace the LEDs.
As for my background I have 2 Masters Degrees in Electronics Engineering and 40 years of experience designing electronics and managing the development of high technology systems.  Much my experience was performing detailed electronic design, which this board would be of the simplest example.