There are several ways to find a professional e-commerce WordPress website developer. Here are a few methods you can consider:

1. Freelance Platforms:
   - Upwork: Upwork is a popular freelance platform where you can find WordPress developers with e-commerce expertise. You can post your job requirements and review the profiles of interested developers. Upwork provides ratings, reviews, and work history to help you make an informed decision.
   - Freelancer: Freelancer is another platform that connects businesses with freelancers. You can post your project, receive bids from interested developers, and review their profiles and portfolios. Freelancer also provides user reviews and ratings to help you select the right developer.

2. WordPress Communities and Forums:
   - WordPress.org: WordPress.org has an active community forum where you can find experienced developers. You can post your requirements and ask for recommendations. Developers often showcase their work and expertise in their profiles, making it easier for you to find a suitable match.
   - WordPress Meetups: Attend local WordPress meetups or WordCamps to network with developers in your area. These events provide an opportunity to meet professionals face-to-face and discuss your project requirements.

3. Agency Websites and Directories:
   - Clutch: Clutch is a popular B2B ratings and reviews platform that lists web development agencies. You can search for WordPress development agencies with e-commerce expertise and review their profiles, client testimonials, and case studies.
   - GoodFirms: GoodFirms is another platform that lists web development agencies and provides reviews and ratings. You can search for WordPress development agencies specializing in e-commerce and explore their profiles and portfolios.

4. Referrals and Recommendations:
   - Ask for recommendations from your professional network, colleagues, or friends who have previously worked with WordPress developers. Personal referrals can be valuable as they come from trusted sources who have firsthand experience with the developer's skills and professionalism.

When evaluating potential developers, consider factors such as their experience with e-commerce plugins (e.g., WooCommerce), their portfolio of previous e-commerce projects, their familiarity with responsive design and SEO best practices, and their ability to meet your project requirements and deadlines. It's also important to communicate your expectations clearly and discuss their pricing structure and terms of engagement before finalizing any agreement.