Sntax Amazing! Thank you for the follow-up :-)

Spidey Linden as I'm sure I've posted somewhere but have no idea exactly where 🥴😵‍💫🙄 the first thing that can be done is getting rid of the 'proprietary' engine from the ancient past and using something contemporary and well-maintained (WooCommerce naturally comes to mind, since, well, it's free...).

The second thing is, well, the search engine. If you want something ready-made which works flawlessly and can be tinkered with, I suggest using Manticore Search, which is free, open-source, and definitely cheap (as in: free!); there are a few tentative integration attempts directly with plugins for WordPress/WooCommerce (such as the 'official' plugin, under development at https://github.com/manticoresoftware/wordpress)

The alternative, of course, is Elastic Search, which also has its own plugin for WordPress.