Most sizeable nonprofits make their financial Annual Reports available from their website. 

To find them, you'll need to go beyond the user-facing options (for example, Buy tickets, Plan your Trip, Donate).  A good place to start is with the ABOUT or ABOUT US link.  Then look for terms like "Financial Reports" or "Annual Reports" or "Reports". 

Another option is to search online for "IRS Form 990" and the name of the organization. Form 990 reports financial information for nonprofits.

See this video for advice on finding a nonprofit organization's financial reports:

"Nonprofit Organization Financial Reports," recorded September 2020, 4 minutes.

NON-PROFIT COMPANIES:

• Article: How to Research a Nonprofit: Deep Dive Approach
  From Bridgespan Group, a global nonprofit that advises and collaborates with philanthropists, nonprofits, and NGO leaders.
• GuideStar
  Information about the activities and finances of more than 650,000 not-for-profit organizations. Requires free registration.
• National Council on Nonprofits
  Includes research, reports, and data on nonprofits and the nonprofit sector
• ProPublica Nonprofit Explorer
  Searchable summaries of tax returns from tax-exempt organizations with financial details such as their executive compensation and revenue and expenses. ProPublica is an independent, nonprofit investigative journalism organization.

Many organizations provide information and research on managing nonprofit organizations. Some examples include: