Direct Answer:
You can't really get cheaper than Upwork or Fiverr or Craigs List. And you'll get what you pay for.
Since you have a starting point (your competitor's site), you could do it yourself on paper: print it and draw your edits, then give it to your front-end dev. (with their code pulled from their page, if you need to).

Longer Answer:
I deal with a lot of startups that hope to build a digital product that's a "better" solution.
I'd caution you: only IF and AFTER you have figured out on your own what your potential customers/users need, and have concluded that the compeitor's site meets (some of) those needs (even if partially) should you use a competitor's actual visual UI/UX design as your starting point Otherwise, you'll just expend effort to make their poorly fitting design less poor. To get and keep customers, you need a GREAT UX, not just a better UX. No customer is happy with a poorly fitting UX that fits their needs less poorly than another business.
Analyzing your competitor's product/service to make your own design fit your customers' needs well, is smart. Copying their design, might not be.

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