$400 Canadian is a good price. They sell here in Australia for around Aus$450. (Aus$1 = CAD$1).
Here is one on EBay in Australia: ZENITH 24T2 CARBURETTOR Ferguson TEA AND TED
When I restored my 1953 TEA20 it was before new Zenith carbys were available. I had my old carby reconditioned, including re-bushing the butterfly shaft holes to stop air leaks. Think that cost me around $160 plus a full kit, new float etc another $100.
Bob in Oz