I found a pair of Amsafe 5 point rotary release belts with Y harness and retractors in excellent condition for 50 bucks each.  Labels stitched on the belts indicate they had been in a 767.   They fit without modification in our Legacy. There is also a position for a crotch strap.  It is a long shot but worth the effort to check the Fly Markets at some of the Fly-Ins.  I have seen similar belts at Salvage Dealers so that is another source.  You might need to replace the webbing but the hardware is the expensive part.  Many years ago when I was building a 320, I posted a fuselage top shoulder harness anchor diagram from Glassair that was in the LML Archives.  Since the Legacy uses that location it would seem to be OK.  Just be careful to measure the angle with a seat cushion and your shoulder and make strong attach points.

Steve Colwell  Legacy