I did find a source. Universal Auger Muffler – DIESELR Corp.
are based out of Alberta. This isn't an 'FTE' but the twister design is a generic one. Otherwise known as an Auger Muffler insert but all FTE/Flo-pro did is put this in a 5" housing and then add a 4" inlet/outlet. You can buy just the aguer if you want oneline other places.
From what I've gathered these don't do much for exterior noise but mostly prevent drone inside of the cab.
I just spent $900 on a new exhaust replacing my 50" muffler and 17" fte with a 'new' setup that was supposed to be quieter but I still have drone at 1000 & 2000 RPM and it's still too freaking loud. It's quieter outside the truck under load than the old setup under load, but now louder inside the cab at certain frequencies. It's also got a nastier rasp at idle at the tail pipe :/
I'm now looking at the Flow-pro heavy duty 8990 4" 8880 FLO~PRO Heavy Duty Diesel - Baffle | 30" Body Center/Center – FLO~PRO Performance Exhaust US (floproperformance.com)
Every shop I've been too just wants to sell me a flow through glass packed muffler and I keep telling them I want it to be quiet yet they keep selling me this 'high performance' bullshit. I'm pretty pissed at the last shop as we had a pretty in-depth conversation about it before he made his recommendation and took my money :/