Yep, IRG has the FN barrels on their US website, go to the sort by manufacturers and FNH USA and then it's a few pages deep. The length is hidden in the description so you have to click on a few before you get the length you want. I think it's 20" first then down in the listed order.
I was looking into the 20" possibly for the future if I go with a SLR receiver set; although still hoping Wolverine is looking into the Daniel Defense S2W barrels in 18.6" configuration.