Good luck on your search! Make it a routine to check common places several times a week.
If your heart is set on an m-sport it may take quite awhile depending on what your ok with in terms of mileage, number of owners, accident history etc.. I saw this recently on C&B. M-sport 6spd was sold for <10k, not bad!
https://carsandbids.com/auctions/rj7...bmw-128i-coupe
For me I wanted purely a project car with a solid maintenance history. msport or sports package, although nice, were not my priorities. Only priority was a 6spd manual. Even with a base manual, these are still hard to find. Maybe only a handful for sale at any given time nationwide.
These cars are already 10+ years old, so it's due time to start replacing shocks, struts, springs, bushings so not having a 10yr old sports suspension was fine with me! I also plan on stiffening up my rear subframe bushings so while I have the rear subframe down, I can add the missing rear swaybar on these base models.
Only regret is not having sports seats but of course not impossible to swap out for sports seats from another e82 or e92, or e92 m3 for that matter
Anyway good luck! It's all about the journey so even during this time in finding one of these gems is all part of the experience.