This is one source - it's the second from the bottom.
http://nxrstoves.com/accessories.htm

You can also order it from Durocorp through Adco or most dealers.

That's good to know, thank you!
I wonder if there'd be any difference between converting a costco "non-LP" to an LP vs getting a propane ready model? Costco just doesn't sell the latter. I'm trying to weigh maintaining the costco ease of returning, vs getting it propane ready from the go. (I live in Alaska so will have to have it delivered to WA and then shipped to me regardless...)

Is there a difference between the NG and LP versions?

Answer is unclear.

All the info I have seen to date from vendor websties and comments in online forums here says that the "propane ready" NXR versions are ones which a dealer has installed the propane conversion kit for you..

The actual manufactuer is Dongguan Hyxion Metal Technology Co., Ltd., and its website seems to say that the stove can be ordered by US vendors with LP fittings. (See link below.)

Since the company sells stoves in job lots, my best guess is that few propane versions are ordered by Duro.

That is just a guess, tho. Maybe you could call Duro's customer service line and ask them. The number is 1-877-639-7264.

Here is a link that might be useful: Hyxion web site

Thanks for the contact info!