Maybe this one? Are you sure the original is a Windline?
Looking at the Maxum Parts Catalog for both the 2100SR (that is what the 2150NF is) and the 1900SR for 1999 the call for a 76830 for the Transom Ladder, 2 Step. From the pics it seems to be a pocket ladder as well.
Then looking at the old to new part number cross reference, the new Bayliner part # for that ladder is 1715851 and described as LADDER, SS, 2-STEP TELESCOPE.
Now Windline does not show a 2-Step version of what seems like would be the correct one but I did find this when searching Bayliner 1715851 (hit was for Jamestown Dist.). Amazon has it a bit cheaper too.
http://www.amazon.com/Windline-Slide.../dp/B000FHGO94
May be way off here but maybe I got lucky and this is the same ladder?
Good luck!
Last option would be to call Bayliner dealers and see if they can order one. If not you may have to call around and find one with some old stock.