I think there is a better way for this.
For the factory, they should have at least standby 1 person at the office to handle customer enquiries through phone or e-mail.
The Trade fair might be important for branding and expose but an opportunity that have came to your doorstep should be grap and follow up and not just reply with busy with trade fair.
Can I put it this way: YOU NEED ME OR I NEED YOU?