Where To Watch Corrections

Thanks and yes you can do this already.  Please see https://help.imdb.com/article/contribution/titles/reporting-issues-with-rent-buy-or-watch-on-link-s/GETY9ULSLNLS3N5S and specifically: 

If you notice an issue with a watch on link or that a product (DVD/Blu-Ray/Instant Video titles only - not video games or books) is available on Amazon.com and our page doesn't include a rent/buy or watch on option for it, please Contact Us and we'll be glad to add it whenever possible.

This approach works for correcting where-to-watch links as well as adding them. 

Hope this helps.