I've acquired 3 Tomy Knapford Station "halves" on TradeMe late last year through separate lots. Two of those halves (making a complete) station were from a bulk lot, and the third halve was from a lot that was an (almost) complete
Thomas Mega Set.
I got the Thomas Mega Set for a good price because the seller just listed it as a picture of the box holding the pieces and I was able to tell from the photo that it was the Mega Set and took a risk that it's contents would prove worthwhile, which it did.
It's worth noting that the smaller Knapford station (i.e. only a single halve) that comes in a set like that is a bit different than the full version - it has signs for all 4 platforms, so if you tried to combine it with another smaller station you wouldn't have a true complete Knapford station because your two signs for each platform would not fit on the same actual platform due to the way each piece is shaped. The signs are sticker though, so if you were super patient and careful you could remove the stickers and reglue them on the right pieces to have a full station.
For me, all 3 halves had the bottoms snapped off or reglued on many of the sign pieces. I was able to use a combination of all the pieces to create a single Knapford station that only has two sign pieces with a broken bit. I tried gluing them back together but they just snap off again when you try to pull it apart again - the base grips the sign pieces too tight so the stress on that part is pretty high, it doesn't take much to break them. Thankfully even with two broken bits it remains pretty stable.
The roof pieces are a little dulled, and the bases a tiny bit yellowed but after a good clean it all looks pretty good. And the trains make a fantastic sound when running through the station.
I think if you are patient you'll see some more crop up on TradeMe. If you do manage to find one then be warned: while it's a cool setup you do need a lot of space and track to accomodate it.