[Koha] linking local book covers to external content

[Haik Zargaryan]

Dear community,

We are uploading our book covers and we would like to link those bibliographic records to some external pages. 

So, the user searches and finds the book in the catalog, opens the record, clicks on the cover image and an external link is opened (e-book of the record). 
Any ideas how to "attach" links to the cover images??

haik.