offer point of sale material - i.e. a stand to display the goods on, posters to raise awareness etc. Supermarkets always like introductory promos like BOGOF.
As Dotwhack says, addiing POS material with the products is a good incentive for them to take them, as is also offering exclusive deals where possible.
Another idea is to help them promote the items when they launch in the shop, i.e. quick note to media saying a particular store is now stocking a certain item (unless it is something quite dull), or to fund a freebie session at peak footfall time etc.