I am trying to find outsourcing firms that can provide steady software development work to my firm on commission basis. Is there a platform for this?

I would start by looking at the apps and software you like to use that was created by smaller firms (not the big companies). Many of these firms also do client work, which you can find out about on their web site. If you enjoy the apps they produce and they have the expertise you are looking for, it can be a great fit. A good example would be a company like Black Pixel.

Hi,
Take a look at UpWork - there are tonns of developers to choose from.

You can take a look at the Eastern Europe' software development market (for example, Belarus).
1. American Gartner experts recommend to outsource software development in Belarus
2. American Business Persons Say It is a Good Idea to Outsource Software Development in Belarus
3. Working hours in the USA overlap with those in Belarus, but not in India or China
https://belitsoft.com/company/advantages-of-outsourcing-to-belarus.html

Outsourcing can be overwhelming at first – each of these sites uses a different system, have a different layout, and can take days to get used to. Also, note that Upwork is formerly oDesk, which merged with Elance in 2013. Check out our comprehensive Upwork review if you want to go into more detail about the platform. Freelancer. Easy to use and suited to smaller jobs – The average job is under US$200, making outsourcing for the first time extremely cost effective for small businesses. Working with a native English speaker is sometimes a good option when you need to be able to verbally communicate project requirements. Guru is also a good option if you are looking to work with a US based provider.
You can read more here: https://www.timedoctor.com/blog/outsourcing-websites/
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath