Most of my first dovetails were cut with a back saw from a small miter box.
One of my current dovetail saws was found in an antique mall.
A lot of antique malls and junk shops have an amazing amount of inventory turnover. That is how they stay in business. Get to know the people at the counter.
Second hand stores and even pawn brokers get some decent stuff at times.
Get to know them and let them know what you are interested in buying. Visit them when you can so they get used to you coming back. You might get to be friends with some of them and be on the hunt for you.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)