I wish it were as simple as directing you to a store to buy a well-priced model.  You can look at Debra’s List for sources for non-toxic couches but they are mostly made-to-order and are expensive.

As for leather, there is no chemical-free leather.  You can read more here about the chemicals used to process leather.  There are safer leather products that use less toxic chemicals.  There is a company called Pine Street Natural Interiors which can make a non-toxic couch using a safer leather.  Read more here.