UPDATE! .... well ... I just viewed some of your other posts about this bike you are restoring. And my tank ISN'T the one you need after all.
It is clearly not the style yours came with once I viewed the copies of the original advertising for your bike.
It surely does look like an Elgin tank that I have. I suppose my Elgin could have been manufactured by Westfield , hence the similarity...
And to boot ... the greens colors are indeed different, between your bike and my tank. Oh well ... I thought I could help but it's not the case.
Good luck with your search! CCR Dave