I currently ride one of the 400 rickshaws in central London and I am looking to get a new one. They cost a lot of money and I would like a company to purchase the advertising space located in the back for £4000. At this price they will get continuous advertising for 5 years.

What is the best way for me to approach businesses and companies and sell my idea?

Other company currently rent advertising space on the back of a rickshaw for £250 a day!
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Your help is much appreciated.