I like your choice.

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This is how I would phrase it, especially as a heading. I'm not all that clear on whether it refers to clients or vendors of theirs (e.g., could mean restaurants that supply them)--although if it goes with previous jobs, it's probably the former.

You'll find lots of refs. to this expression in a catering context, for example:

The Blue Rock Catering Group is a market leading catering and events company, with exclusive contracts with spectacular Sydney venues such as Fort Denison, Cruising Yacht Club of Australia and the Australian Museum.
http://www.statetheatre.com.au/about_websites.html

Meal delivery and catering service. Provides on-line and phone order meal delivery from leading restaurants. Company has exclusive contracts with restaurants. Company also provides large group and corporate catering.
http://www.mergernetwork.com/static/details/24565.htm

The group also has another 6 restaurants and cafes, including Sit!0, Romamor and Espresso Bar plus the catering division, which recently secured the exclusive contracts for the GSP stadium, Finance Ministry and Police HQ.
http://www.xak.com/main/newsshow.asp?id=26792

"Before the Carriage Room, you had to depend on what the racing schedule was" to put on a large function, said Brian Handleman, founder and president of Maryland Turf Caterers, which has long-term, exclusive contracts for catering at Pimlico and Timonium race courses.
http://209.116.252.254/4_2002/18.html

It is correct.Best of luck!
However,the other people ideas are also great,it´s up to you,best of luck!