There are others, but we like the folks at Belch.io, StephanieOGayGarcia, and Web Canopy Studio. That being said, if SEO is a major concern you'll probably end up having whatever you settle on customized/optimized by one of the folks above.
-ps Recently began working with a visually impaired client who is helping us understand some of the gaps in accessibility they typically encounter on the web. Not related to HubSpot specifically, but certainly a factor when considering UX -- an increasingly impactful ranking factor.
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