Convert your rear turn signal lens using
a HD FLT red lens.
The first lens I observed that would fit our turn signal light housings were some
at Star Days 99' on Barons table. Prices on these lens were $10.00 a piece.
I had seen a few post that said a Harley lens would work but never saw a part number so
off I went to local cycle shop "Rodneys Cycle House" here in Little Rock.
I found a FLT red lens made by Custom Chrome that fit if I flipped the trim ring over and
it fit perfectly in the backside of the trim ring, the drawback I though would be that the trim ring just set in the lamp housing and did not have a water tight seal. Later now, I've found out that this has not been a problem as the Barons did not seem to have a water tight seal either. 
The last I heard  the supply of lens from Barons has been depleted and no longer available.
Here's your chance to have a nice looking red rear turn signal lens....
Happy riding  **Mr. Tidy**
OHNO11 said in a post that
   Heres an old Yamaha Part# 341-83332-70 for red lens, some dealers may still
   have some , fit all star line bikes, just remove trim ring on stock lenses..
The first step is obtain the lens.
The Lens I used were made by Custom Chrome with he number 26-126 upon the label, it specified that it fit a FLT Harley
Davidson.
I purchased them at a local Cycle shop
catering to HD, Price $3.95 each
Remove original amber lens, 
Remove trim ring, notice the cut out that fits
over the lamp housing stem.
Flip the trim ring over and put the cutout
towards the  bottom of the housing.
(the trim ring just sets in the housing cradled
and will be held by the new lens and screws)
Next put the new lens in place and use the original screws to secure the new lens in place .
 The new lens and trim ring is not sealed
as was the original lens by the rubber gasket.
The bike show has been converted for approximately 8 months and has had no problems with water due to rain nor washing.