I think the question here is really, “what do you have to hand?”.
Chain axes can be acquired but if you’re having to buy another kit to get them then you may as well get the FW one which will fit perfectly to the Escher models.
If you’re scouring eBay then you may find a part or two but don’t pay over the odds - the better bet are 3rd party bits manufacturers who will have stuff like that.
Alternatively, get some plasticard (or thin plastic packaging) and make the blade yourself and glue it to a suitable handle. It’s two flat sides in a roughly D shape and a third, slightly larger one which you cut little triangles out of. Sandwich together with glue, stick to pole.