Personally, I'd seek out the flea markets.
I often find old chisels and drawing knives. Usually covered with surface rust, but that's easily fixed.
There is almost no market for old tools here, and people on flea markets often sell their grandfathers' tools when he passed away. Generally, the price for any old tool is between 50 cents and 2 dollars (unless the seller is a merchant).

I've bought a couple of antique sheffield chisels for a couple of bucks.
A blacksmith's hammer for 90 cents.
A huge handmade rasp (with irregular aligned teeth) for 1 euro.
A huge nicholson file, never used. For 1 or 2 euros...

As long as the temper is still good, an antique chisel will serve you as good as a new craftsman chisel which costs 10 to 20 times more.