Way To Connect/Match Existing Etsy Listing SKUs To (Also Existing) Shopify Products?

Can’t seem to find this solution anywhere and am desperate for an answer!

Every software/tool is either way overpriced or does significantly more than I need it to. I really just need a one time thing, not another monthly subscription.

Essentially, I need a way to match/pair up existing Etsy and Shopify inventory — Not to migrate/import. My inventory exists on both Etsy and Shopify already but I am looking for a better way (than straight copy/pasting hundreds of SKUs manually) to update my Shopify product SKUs to reflect my Etsy listing SKUs. Specifically and ideally, some kind of a visual mapping would be helpful. Or a way to say “Hey, this Etsy listing = this Shopify product. Pls reflect the SKUs for each variant accordingly”

I feel like this should be an easier thing to accomplish but also have exhausted my search to find a way to make this happen. Anyone have any ideas?

Thanks in advance!