A lucky find at the supermarket today: plastic carriage in nearly perfect 1:12 scale (as modelled by Marie, a Merrymeeting collectible doll).
Not bad for $5 (and I bought all five of them).
The purple seat section unclips easily. I'm looking forward to trying to convert the carriage base & wheels into more gypsy-looking little wagons.
The horse is a nice shape, but shiny plastic. Hopefully I'll get around to studying the flocking tutorials out there to turn it into something more elegant!