If you have use the product type instead of vendor, you would need collections where the handle matches the type such as:-

/collections/jewellery matching product type handle of "jewellery"

Then instead of this:-

{%- assign vendor_handle = product.vendor | handle -%}

You can use:-

{%- assign vendor_handle = product.type | handle -%}

Which will look for a collection matching the product type.

More info on handles if useful:-

https://shopify.dev/api/liquid/filters/string-filters#handle-handleize

https://shopify.dev/api/liquid/basics/handle