For small businesses in niche industries, the best B2B marketplace depends on your target audience, product type, and region, but here are a few top choices:

1. Pepagora

Ideal for businesses in India, especially Tamil Nadu, Pepagora focuses on connecting regional manufacturers and suppliers with buyers. It’s known for niche segments like textiles, sports products, and industrial tools. It supports localized marketing, making it perfect for small businesses trying to grow their presence in southern India.

2. Alibaba

Best for international reach, especially if you're in manufacturing or wholesale. It caters to a wide range of niche categories like eco-friendly products, custom components, and more. But note: competition is high and it often favors bulk-oriented suppliers.

3. IndiaMART

One of India’s largest B2B marketplaces, IndiaMART supports many niche industries including healthcare supplies, laboratory tools, and agriculture. It’s user-friendly and offers lead-based selling, which works well for small businesses.

4. GlobalSources

Great for niche electronic products and components. It’s widely used by tech-focused small businesses looking to export or connect with international clients.

Bottom line:
If you're a small business in a niche industry, start with local or regional B2B platforms (like Pepagora or IndiaMART) to build traction, then gradually expand to international ones like Alibaba or GlobalSources as your capacity grows.