I would remove the seat and look at the linkage. Parts should be available at the junk yard. The nuts require an ep18 socket. An e20 or a 15mm six point socket will work.
They will probably try to sell you a used seat. If your seat is good ask for a seat that is worn out but has good linkage.
http://www.ebay.com Search 131047826837 This is a picture of an EP18 socket