An antique dealer is the absolute last place you should ever look for something old at a good price. If you want a straight razor you should go to every "Estate" sale you ever see and visit every barbershop with any barbers that are over 60 years old. Another good option is to visit "flea markets", but they are long shots.

Another good option is to go out on Ebay and do searches like "staight razor" instead of "straight razor", leaving the r out is the "Einstienian" moment in Ebay searching. Also, don't look for a nice razor, look for nice blades and nice scales separated. You can put them together yourself.