Genuine Boeing 757/767/747-400 rails for Ipeco cockpit seats.  If you could find a set, they would sell for $8000 per cockpit set if bought used from a dealer...no joke.  These can be adapted for use with 737 IPECO seats.  The width of the seat stop section is slightly wider than
the 737 rail of similar function.  We have sold a number of these to 737 sim builders and sim companies, all were adapted pretty easily.
 
$1750 cockpit set for 2 seats.
 
We also have 2 sets of 747-400 seats that use these rails.