LOTS of vendors will NOT sell in MA any more, but do work the NH shows.
The NH show is 120 tables, 1/2 the size of Danvers.
Danvers is a new venue and very small for Carole's shows so many may take a "pass" on it.
Many shops are relatively small and can't split up their inventory and staff to work two shows on the same weekend. So both shows can suffer when competing.
No idea how this will shake out, but don't expect anything like you saw in Marlboro!
1919 parts I'd expect to see more of at someplace NOT-MA.
Zero Hour Arms (call them) may be a source for 1919 parts that you need (not at a show), as they specialize in the less popular guns.
I'd also give Collector's in Stoneham a call as they sometimes have some oddball items and some 1919 parts hanging around behind the counter wouldn't surprise me at all.