Not any more. I used to buy them from Allied for a few bucks, when I was a kid. More recently, I was prowling through some dusty bins at HalTed and found one full of TDs. They didn't know what they were... just wires with bumps. 10 cents each.
RCA made TDs with peak point currents over 100 amps, but I don't think they found any good uses for them. The only germanium tunneling parts still made in any volume are RF detector back diodes.
GPD bought the old GE td process, which was insane, but they don't seem to make them any more. Maybe somebody else got it.
John