SQL Server Express Edition Primary - Secondary Model From Replication Considerations (SQL Server Express) in Books Online, SQL Server Express Edition can only act as subscriber, and only by using Windows Sync Manager.
Can anyone suggest any other methods or third party freeware tools available to produce a Primary - Secondary model like transactional replication between two Express Edition instances?

It must be free.
It must not use triggers.
I cannot build a separate application for this.

I'm searching for freeware or a tool like SymmetricDS, but unfortunately SymmetricDS adds too many triggers. For 20 tables, I had more than 100 triggers in my database. Moreover, those triggers will be considered as malware in concern with security. It does performance degradation too. Still, when there are triggers that track down what are we doing, it will be a security concern, because we can't provide 100% assurance that tracked data will be secured as it's the business logic of SymmetricDS. And moreover, I am not going to use  that product, so talking about it over and over won't solve my problem :(
An answer to Replication from one SQL Server Express to another on Stack Overflow offers some suggestions:

In summary (from the link):


Write an application that transfers "articles" from your "publisher" db to your "subscriber" db(s).


OR


Create a set of views to have a summation of data that you want to be
published. Then create INSTEAD OF triggers on these views (you can't
create an AFTER/FOR trigger on a view) to process that data and
transfer it to your "subscriber"(s).


Triggers On Views? What For? by Michael J Swart has some good information on view triggers.