Replicate to a secondary database that also allows edits
If you need bidirectional synchronization, have a look at merge replication. (Good introduction: http://www.sqlservercentral.com/stairway/72401/) 

However, you question sounds like you don't want those changes to be applied to the master sales database. In that case I would setup shadow tables that take the changes and use replication to load the master tables. The logic to write to the shadow tables and read from the shadow tables if there is a row, form the master table otherwise could be placed in a view with an instead-of trigger. The following is a conceptual example of that model:

create table dbo.product-master(Id int, ...);
create table dbo.product-shadow(Id int,....);
GO
CREATE VIEW dbo.product
AS
SELECT m.Id,
       CASE WHEN s.ID is NULL THEN m.col1 ELSE s.col1 END AS col1, --show shadow row if it exists, master row otherwise
       CASE WHEN s.ID is NULL THEN m.col2 ELSE s.col2 END AS col2,
       CASE WHEN s.ID is NULL THEN m.col2 ELSE s.col3 END AS col3
FROM dbo.product-master m
LEFT JOIN dbo.product-shadow s
ON m.Id = s.Id;
GO
CREATE TRIGGER dbo.product-IUD INSTEADOF INSERT,UPDATE,DELETE
AS
BEGIN
  --use INSERTED and DELETED virtual tables and the MERGE statement to apply changes to the shadow table
END;
GO


To load the master tables you could use any kind of replication (see link above for an introduction).