The other thing to consider is whether braille printers even use a font at all. A font which prints braille on paper using a LaserPrinter would be of little use to the blind, and I can't see postscript or truetype outlines being of much use to a dedicated braille printer.
There are a lot of English braille fonts out there. Are you saying they are not functional?
If by “English Braille fonts” you mean fonts which have Braille characters encoded in the Basic Latin range, then I imagine there are lots of those in the same way that there are lots of non-roman fonts which map non-roman characters to the Basic Latin Range. Most of these are legacy fonts which predate unicode. Whether they are functional really depends on your definition of 'functional'. If you mean, “can they be used”, then I suppose so as long as you're not planning on exchanging any documents in a usable electronic form. But this is a poor solution for anything being designed in the 21st Century.
I'm not sure I understand what you mean by the letters being RTL even though the script is LTR. Individual letters don't have a direction.
What you need isn't a special font for Persian Braille since the Unicode Braille Patterns range (u2800-u28FF) should cover all variants of Braille. What I think you're really looking for is a keyboard layout for Braille that mimics a standard Farsi keyboard layout.
SIL International has some utilities for designing keyboard layouts. You can find them here: