How to target keywords not found in product description

I've made beautiful (in my opinion) product pages for a range of hoodies on my shopify site.
So far I've managed to reach page 1 on google for my target keyword but I want to start targeting other keywords.

I've identified a similar product/keyword that I want to target. Strictly speaking this keyword isn't exactly what I'm selling but I'm confident that buyers may consider my product over the actual product they are searching for.

My question is how do I start to target this keyword without changing my product page?

I hope I've explained my question without being too vague.

Appreciate any support.

In terms of off-page SEO you build links with your keyword as anchor and LSI for that keyword. For onpage, maybe build a blog alongside your shop where you can promote articles with that keyword? Maybe add that keyword somewhere into the description of the product, where it would make sense? Maybe add the keyword in a picture's title alt?

If it's not the same thing then you're talking about a different search intent here. You need to focus a different page for that keyword, otherwise, you can mess up your existing rank and end up with nothing. As you're already on page 1 for it, I'd be very careful of what changes you make to that page.

If you can't exactly create a sales page for it, maybe you can go into the product comparison direction or review type where "why this product is better than this" and you rank that page. From it, you can forward users to the main product page.

Really depends on the specific keywords you're talking about.