After spending a couple of days in Linocln, NH and learning about a 1942 crash of a B-18 in the area, it got me thinking more about the aircraft (plus it’s an interesting story).
I think White Eagle produced a Vac kit in 1/72 many moons ago.
Charlie
Nothing in production. Been searching for old OOP kits on eBay for a few years now myself.
I think… don’t qoute me on this… that Williams Bros made one a long time ago. I might be getting loopy off of the paint fumes though…
Ah, after a Google seach, I found the UK Hannant’s site lists a future release from Special Hobby - so it may be a while before we see it:
http://www.hannants.co.uk/search/index.php?FULL=SH72095&ADD=SH72095
Williams Bros made a B-10, but not a B-18. Fightnjoe, from this forum, has been eagerly awaiting someone, anyone, to produce a styrene version of the Bolo. Just ask him 
Ahhh! Now that you mention it, I do remember the B-10. I must have gotten mixed up. It happens alot these days…[D)]
If you do find a B-18 kit, find the best C-47/DC-3 kit for the wings and tail as that is what it was designed from.
I think it was AModel (or AirModel, not sure) that produced the vac kit of it. I picked it (B-18) and a C-117 (Super DC-3) off EBay several months back, both in 1/72. They definately are rare as I’ve only seen either ever listed one other time, and the fact that I shelled out $30+ a piece for them. The B-10 was only the fuesalage, requiring a donor C-47 / DC-3 kit for the wings and tail surfaces. They got sealed up and put in storage with a good portion of my kits waiting for their turn on the bench