Okay, this may be not quite enough info for you but ...
When I worked for Janome (last year) we offered a treadle machine. There is a decent demand due to areas without electricity. They had similar functionality to the mid end machines (zipper foot, button holes, zig zag etc.)
We started offering them due to several dealers saying that they were spending lots of time retrofitting the electric machines
So ... not a lot of info, but it does give you something to go on.
The Janome Treadle model was the 712T and generally sells for a little over $200.
edited to get the model number and the price in there for you