How does a small website procure coupons to display?

I am starting a website for my local town and I want to show coupons as a feature for my customers to print and use in local stores. I can may be talk to a few local vendors to promote thier coupons on my site but how do I get manufacturer coupons that can be used in grocery chain sort of shops. I searched a lot online but could not find answers. Please help.

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