Licensing Image

I work in e-learning and need to purchase images for clients that will be used in their online courses for their employees (not for resale).  We do not retain rights to the images, the images are in an online course and are not printed, and the client is the one who need the right to use the photo.  Is there a license level or a way to purchase that allows me to "reassign" the right to use the photo from my company to the client? Or would they need to purchase the stock image so they have the right to use is? We want to make sure we are using your services properly and I don't see a way to do this in your licensing agreement.

Thank you.