The part you mentioned is in chapter 21 of:
www.fanfiction.net/s/3999495/1/bBirth_b
Birth » by cutebaby reviews
Sesshomaru's ownership of his multi billion dollar company is threatened. With only a year to produce an heir and no mate, or desire for one, his advisers come up with the perfect plan, cloning. But what happens when the experimental baby goes missing?
Inuyasha - Rated: T - English - Romance/Humor - Chapters: 30 - Words: 239,081 - Reviews: 1148 - Updated: 8-24-09 - Published: 1-7-08 - Kagome & Sesshomaru - Complete
I hope this is what you seek.