<s>Lapua Scenars were never made by Berger or Sierra.
Lapua = Company/brand
Scenar = model name</s>
Berger = 300gr Hybrid
Sierra = 300 Match King
Now, ammunition companies:
Lapua still makes and sells (in the US) 338 Lapua Mag ammo loaded in their brass with their bullets (250gr and 300gr Scenars)
Federal makes 338 LM ammo loaded with 250 Sierra Match Kings and I think you might be able to troll up some 300 SMK ammo too
There is a little bit of Federal floating around from a PSR submission that's loaded with 300 Bergers, it's rare though.
Hornady makes an excellent shooting match option, 285gr BTHP Match ammo and it is about $2/round cheaper than Lapua ammo and $1/rd cheaper than Federal ammo.
Custom ammo manufacturers can make it for you, here are a few with rapidly growing positive reputations:
Dallas Custom Reloads
Southwest Ammo
Copper Creek Ammo
ETA: I mistakenly read your thread as if you were looking for someone other than Lapua to make 300gr Scenar ammo.
Berger and Sierra make 300gr 33 caliber projectiles and Hornady makes an excellent 285gr version as well.