Hi, I've been following your post and think I might have some useful information. I told you before about the Deluxe Flyer I was restoring but haven't finished yet, and this one still has the original factory toolbox. Below is some pictures that you might could use for reference, and if ever you need some dimensions or details or something, I can help you out with that. One thing I will mention, is that this is the only surviving example I've ever seen of the original toolbox tank used on these bikes in 1916-18. Around 1920 and later, deluxe flyers were furnished with a slightly newer style toolbox tank, as seen in the last image (says elgin on it, but it is just to give you an idea of an option you could go with). One nice thing about the later style tank, is that it is much more well built and sturdier. The earlier style like I have, is literally soldered together at the seams, and made out of a single cut piece of sheet metal folded and soldered into shape. It is as weak as a cookie tin, and I had to totally rebuild it for my restoration. It might not be too difficult to fabricate a replica of the original at home even. The later type is nice though, because it is thicker, stronger metal, has better latches and hinges, and is crimped together; it is also much easier to find one for sale, maybe around $200-$300 or so. Hope this helps a little.