The Good2Give Workplace Giving platform is not open to the public.
All employees of companies registered with Good2Give are eligible to donate to you. If you go to https://workplacegiving.org.au/enabling-giving/workplace-giving-platformand scroll to the base of the page you will find see the companies who use the platform.
There are over 3,000 charities registered on the Good2Give Workplace Giving Platform.