I'm pretty sure you mean SFI, not FFI. Just to give you the background, SEMA, or Specialty Equipment Marketing Association found the need to police itself and so founded the SFI, or SEMA Foundation, Incorporated. SFI is charged with testing aftermarket products and certifying them to meet certain standards. SFI specification 18.1 is the standard for high performance harmonic dampers.

You can find them at any speed shop under a variety of brand names. Popular online shops would include www.summitracing.com and www.jegs.com

Here's a link to Damper Doctor that I have recommended before. Email them or give them a call and tell them what you need.
http://www.damperdoctor.com/High_Performance_Damper.htm