I’m the author of Advanced AJAX Search & Filter. It has the unique features that you will find it’s easy to integrate to your theme.
So, instead of create totally new searching function, now you just need to use the plugin, embed to your theme, and it works!
I’m happy to support you guys everything or what you need.
This is my plugin: https://codecanyon.net/item/advanced-search-form-builder/20492445
You do not need extended license to use my plugin, just have the banner on your product descripton, that’s all good.