'84 FLT flasher

Pretty much looks like a standard flasher from what I can see.

 

Try a standard heavy duty flasher, leaving the male 5OJ wire off. When my flasher went bad on my 99, the original was expensive, the Dealer gave me a standard cheaper flasher. I can’t remember if there was a Pigtail adapter involved or not. Either way it worked, and just laid in the fuse box, instead of being mounted. Looks like yours has already been adapted. Hope that helps

 

I know you can get a 4 post flasher relay at NAPA..

 

Didn’t know FL used 4 pin flashers.
Just use a heavy duty 3 pin. One is 12v hot. The other goes to the switch on column. The center is the pilot signal for the dash or the signal stat switch indicator light on column and is not really needed for the flasher to still work its magic.

 

One thing I just thought of and should have mentioned was the 3 prong flasher prong pattern is the same as an old school three prong high/low head light bulb socket. Get a good used one off of a parts car or truck or Dorman makes replacements in their “Help” line. Every old truck I encounter has had the flasher just hanging somewhere with 3 individual wires connected to it. The socket cleans it up nicely.

 

Maybe at one time in it’s past life it had auxillary strobes or flashing lights mounted on it somewhere or pulled a trailer that required them? I found a 3”x3” box with 8 prongs on it in a truck once hanging under a dash by wires going to nowhere. Researched it and found it was a wrecker truck strobe flasher made by signal stat in the 1960’s. Obsolete almost 40 years. Lol!