I actually stopped in at the Grahame Fowler store in NYC for the first time three days ago. The shop is TINY, but the staff was very friendly and they had a lot of special make-ups, as well as some standard models (mostly with leather soles). Their prices are a bit high (so at the end of the day they are close to a lot of the UK prices after tariffs).
I've also found Trickers in the US at Leather Soul (Honolulu and Beverly Hills), and at Haberdash in Chicago. LS Honolulu's stock was a little thin last time I was there (early this year), but supposedly they have a shipment on the way.
Maybe Zippy knows of more US sellers?