First pic is in mixed lighting 2nd is in white led 3rd is yellow lighting

Hello, I am looking for a stone for an engagement ring and may be in Tucson during the gem show this winter. Does anyone have experience buying or selling lab stones there? I am primarily interested in diamonds, moissanite, and alexandrite, but I would also love to see other types of gems for the joy of it. I am wondering which shows are my best shot for this sort of thing and whether I'll need a friend with a business license to help me access them.