SourceLink started as KCSourceLink in Kansas City with initial funding from the Kauffman Foundation. Today the KCSourceLink affiliate is partially funded by 12 of Kansas City's largest corporations (AMC, Hallmark, Sprint, etc) who have each committed $12,500 for five years. This funding was used as match to access a grant from the U.S. Economic Development Administration.
Our affiliates are frequently financially supported by city, state, or county agencies. Examples include: City of Baltimore, Winston-Salem Chamber of Commerce, Loudoun County Economic Development, Iowa Economic Development Authority, and Mississippi Development Authority. Currently, we do not have any affiliates receiving direct financial support from SBA. This said, foundations like JPMorgan Chase provide support in select metros where they have strong presence.
We would recommend you explore local corporations, the U.S. Department of Commerce Economic Development Administration, bank community reinvestment act funding (keep in mind this will likely only come in $5-10k at a time), local foundations interested in entrepreneurship and individuals. You might also ask serial entrepreneurs looking for opportunities to give back.
For more ideas, here is a powerpoint from one of our last conferences that covers resources which we typically advise groups explore for funding ideas.