I feel that you be missing out on a great source of new business !
You current clients !
Call them up and ask for referrals.
It's a simple task really.
'Hi Bill ( for eg ) I'm glad that we got the last lot of leaflets out for you on time, have you been happy with our service so far ? Bill I was wondering if you have the names of 2 or 3 other compaines that you think would benefit from our services ? '
Chances are that they are happy with you service

, so will have no problem giving you the information .
Always ask for '2 or 3' they will most likely go for the lowest denominator here but this still gives you 2 new prospects.
Give them a call, introduce yourself and let them know that Bob has been happy and thought their business could benefit from your service too.
Whether you get the new business or not, call 'Bob' back after a couple of days and let him know how nice the 2 prospects were, then once again ask for 2 or 3 more names of people.
The power of referals based on your current clients should never be ignored in business.
Look after them, send them small gifts if you do get new business from the referral.
Repeat this process and it will be one of the most valuable marketing activity you will ever do.
Paul