Where can I find a grant for a nonprofit charity?

That depends entirely on what type of work the nonprofit charity has historically done and/or is interested in doing in the future. For example, an international nonprofit involved with healthcare infrastructure in developing countries might contact the Bill and Melinda Gates Foundation. A nonprofit operating a city homeless shelter and/or food bank might research grant options from the city, state, or county governments, or perhaps from local religious institutions. Part of the process is discerning the nonprofit's field of expertise and impact, then networking with appropriate funding sources.