you don’t specify the kind of organization and the event or activity you would want to be sponsored. Anyway, Community Tool Box may have some useful indications for you, f.i. in Chapter 46 Planning for sustainability, and particularly in Section 3. Promoting Adoption of the Initiative's Mission and Objectives, on the web page https://ctb.ku.edu/en/table-of-contents/sustain/long-term-sustainability/promote-adoption-of-mission/main
There are operational ideas also in Chapter 33 Conducting a Direct Action Campaign https://ctb.ku.edu/en/table-of-contents/advocacy/direct-action/letters-to-elected-officials/main which may be interesting if you need to contact possible sponsors for funding a particular event.
Best greetings, and wishes for your organization!