The Runoffgroove Ginger is a wonderful sounding pedal that was modeled off of an Ampeg SB12 fliptop (not B15, but close, especially in a pedal format). You should definitely put it on the list for consideration. They're fairly easy to come by, and since it's an open design, it's relatively affordable when you do come across one: GINGER VFE Pedals is the only company I know of that most recently used to build this circuit. I had one that was built by @Dominic DeCosa, and used it for many years--highly recommend it.