There was a time, not so long ago, when you couldn't move for 12 back vaders on sale.
All the ESB ones do exist MOC, with the 45b being the most common...but that's only in comparison to the other three. Took me a while to find one.
I've seen maybe 6 45a's, have owned 3.
I know of 2 41 backs and 2 30 backs.
Comfort yourself with the knowledge that you got the 12 back. That by far is the coolest looking of the lot.