Ecwid by Lightspeed Developer Needed – Copy Funnel & Create Direct Buy Now Checkout Flow

I am looking for someone experienced with Ecwid by Lightspeed who can help me set up a direct checkout funnel.

Please watch this Loom video carefully before applying:
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The task:

I have a funnel / landing page that needs to be copied as close as possible / 1:1 from my reference. The page will have a Buy Now button.

When the customer clicks the Buy Now button, the correct existing Ecwid product should be added automatically and the customer should be redirected directly to checkout, skipping the normal cart page.

Important:
I do not want a one-time checkout URL or payment link. The Buy Now button must be reusable and work for every customer, even with multiple customers and repeated sales.

I am using Ecwid by Lightspeed directly. Wix is only shown as a reference example for the flow. In the Wix reference, the Buy Now button is connected to a product and sends the customer directly to checkout. I need the closest possible version of this in Ecwid.