Here are some options to find idea brokers, invention agents, and other professionals who work on commission to help develop and market ideas:

Inventor's Digest Database: This is a large database of invention promotion companies, brokers, product designers, etc. that work with inventors. Many operate on a commission model.

Invention Connection is an invention marketing company that connects inventors with brokers, agents, manufacturers, and retailers. They vet the professionals in their network.

SBA List of Invention Promotion Firms: The Small Business Administration maintains a list of registered invention promotion companies. Review complaint histories carefully.

InventRight Directory: InventRight vets invention marketing companies and maintains a searchable directory. Many work on a commission basis.

Engineer's Directory: Search engineering firms, hardware and software consultants, and prototypers who may be open to developing sci-fi or futuristic ideas on commission.

Futuristic and Sci-Fi Forums/Subreddits Post an inquiry on forums and subreddits focused on sci-fi, futurism, and technology to find creative individuals open to speculative projects.

LinkedIn: Search and post inquiries targeting professionals with relevant engineering, technology, and science backgrounds who may have an interest in improbable concepts.

Angel Investors/Crowdfunding Sites: Pitch speculative concepts to angel investors or crowdfunding supporters to secure funding for professional development.

Thoroughly research any individuals or companies before sharing your idea in detail or providing funds upfront. Establish clear contracts/agreements.