Finding a qualified custom software developer or developers can be crucial for your business. You can hire internal developers who will work directly in your company. This will allow you to have full control over development and faster communication. You can contact specialized software development outsourcing firms https://www.sombrainc.com. They can provide you with a development team with experience in your field, and this is often a faster way to get results.

You might post the job description in freelancer marketplaces: I have accounts on peopleperhour.com (UK) and upwork.com (US) for instance, the other big one is freelancer.com.

In HN there is the monthly Freelancer board: https://news.ycombinator.com/item?id=37739027

In my profile you can find my website and there my contact information if you want to discuss the job directly with me.

There are a host of software consulting companies that can help you. There are also free Lancers if the scope is small.