Is it possible to override a ReadCommittedSnapshot isolation level with ReadCommitted isolation level for a particular transaction?
There is no way to override the database-level setting of read committed snapshot (RCSI) for a whole transaction.

When RCSI is set, all read committed transactions will use row versions, delivering the last committed version of a row.

A session-level override option has been asked for. You can vote for it on the product feedback site at Add SET TRANSACTION ISOLATION LEVEL READ COMMITTED LOCK.

You can override the setting per-statement and per-table using the READCOMMITTEDLOCK table hint.

Alternatively, you could use snapshot isolation (SI) and turn read committed snapshot isolation (RCSI) off. Each transaction would then either SET TRANSACTION ISOLATION SNAPSHOT or SET TRANSACTION ISOLATION LEVEL READ COMMITTED.

More information in my series of articles on isolation levels.