under your CTA, or above the buy button if it's a Shopify store write these exact words for an uplift in CVR
"Please add to cart now. If we are out of stock, please check again in a few days"
@Alodehx just posted a SL/advertorial on a beetroot powder I wrote a few years ago that wasn't put to use. You may be able to get some ideas from it. Good luck!