I can offer you a 728 x 90 top of pages banner on a website that gets an average of 300,000 visitors per month.
the cost of the banner is 1,500 USD for 30 days, the banner will be up all the time during this period, and it would not be shared with other business ad.
I have two websites with the same amount of visitors, if you are interested I will give you the websites links to view their details on Alexa.
I also have a website with 70,000 visitors per month, I can offer the banner for 500 USD.
I need to find out your websites details on Alexa to give you an estimate of the improvement you would get.