The agency will be tasked with developing an online media strategy for the retailer, which launched four years ago and has 80,000 visitors a week to its website.
Marketing activity will begin immediately in a bid to drive sales of I Want One of Those's range of gadgets, gifts and lifestyle products in the run-up to Christmas.
Matthew Giles, commercial general manager for I Want One of Those, said: "We're pleased to be able to inject fresh creativity in our approach to both marketing and public relations and we look forward to seeing the positive effect on both brand awareness and sales."
I Want One of Those has also hired Hill & Knowlton to handle its PR account as it tries to build awareness of its brand.
Carl Walsh, account director at Manning Gottlieb OMD, said: "Through the management of online media planning and buying, including affiliate, network and portal deals, we will use our experience to help I Want One of Those move forward and grow."
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