If you are looking for a developer to hire and code this solution for you, I would suggest checking out our Shopify experts directory. With that said, if you are willing to try your hand at it yourself, there is an older thread here that has some provided code that you can try implementing within your theme.
With that said, if you do decide to try it yourself, be sure to duplicate your theme first! Just in case you break anything, you will have a copy of your theme before you made adjustments.
If there is anything else I can help you with, please let me know.