Speed throttling only occur if the battery are totally not recognised.
Under "Service Battery" notice, you should still able to use the unit normally. Provided the battery does not expand of other anomalies. The notice will change to "Replace Soon" and "Replace Now", by then only you are advice to replace the battery.

The notice will not go away until you replace to new battery. Just live with it for now till you decide for new battery. Example, the battery still charge and performing fine.

These are non-retail purchasable part. You need to contact the service centre directly. We do carry full range of replacement battery if you are in KL.