If you're looking for an alternative to GPT-3 for chatbot development similar to the Pro version, one option you might consider is OpenAI's GPT-4. OpenAI periodically releases new versions of their language model, each one more advanced than the last. As of my last update, GPT-4 has not been released yet, but it could offer even more capabilities and improvements over GPT-3.
Another alternative is Microsoft's Turing Natural Language Generation (T-NLG) model, which is also known for its advanced natural language processing capabilities. T-NLG is a large-scale AI language model that can be used for various tasks, including chatbot development.
Additionally, there are other AI language models developed by companies like Google, Facebook, and smaller AI startups that you could explore for chatbot development. It's always a good idea to research and compare different models to find the one that best suits your specific needs and requirements.