Two emails that I received from the ARK folks about a month ago:
"Yes, we don have them instock, It is new product that we’re going to list online soon. But if you like to purchase itemplease contact us at 909-947-1275 ask Michael"
AND
"Yes, we do have the GRiP Exhaust now available for the FX50 models. Right now we only have them with the polish tips.
The MSRP price is $1999.00 and I can offer you a price for $1599.20 + $159.00 S/H within the lower 48 states.
If you are ready to place an order or have any questions, please call me M-F 9am-5pm PST
909-947-1275?
It appears as though it's a distinctly different product that's being offered for the 5.0.