The most renowned bot isn't even available to the public. And the one that is publicly available is known to be unreliable, working only sporadically. Finding and hiring a proficient developer for a custom bot can be challenging and expensive, and that's without factoring in the high maintenance costs.
Hiring and managing chatters who charge more than $3 per hour can be a bit of a headache. Many agencies face issues with chatters either stealing leads or suddenly disappearing. So, automation might be the more optimal solution, even if the conversion rate might not match that of human interactions.
I'd recommend posting in the "WTB" section or exploring the marketplace. Best of luck with your search!