My DD found my first treadle in a thrift store. It is in good shape cosmetically but does have some issues. It needs the head cleaned. The needle doesn't move but the treadle and wheel work great.
I posted a want add on Craigs List and found my second one. It is in very good working order and has six drawers instead of 4. I only paid $75 for it.
I have one more treadle but it will be going to a new home soon. It is a 1873 America #1 treadle. I only paid $50 for it. I found it at a yard sale.
You might want to check with antique stores. Our local stores had an auction and sold several treadle for $25 each! My heart sunk when I found out.