I need someone to make list of digital marketing agencies in the dental niche

I need someone to make list of digital marketing agencies in the dental niche

I need someone to make me a list of marketing agencies in the US/UK/AU/CA that deal with dentists as clients, dentists or dental clinics, good option is to go into dentists / dental clinics sites and see who is marketing agency (usually is seen in the bottom) - web development companies also relevant, but must be in the niche

This is a custom job and I need someone to do it manually and do it good, I expect list to be 1000 emails minimum

Thanks!