Potentially you could gather purchase commitments that are explicitly contingent on being able to be processed through GLO... Potentially you could offer inducements to the companies that accept GLO, such as an advertising deal with Google Maps or Waze that is like "Spend your GLO here at taco bell on a tasty cheesy gordita crunch." Idk
I think there is a bit of a problem with the "favor" mindset and too much of the onus is put on the person seeking help.
People with power, money, connections, and influence, to the extent that they are EA, should use these capabilities for good, and often this can be through helping other EAs (or people, for that matter). Such big people are extremely busy, but this probably means that they should have systems in place to help them deploy their capabilities to effective uses. If this means hiring someone or referring someone else to screen requests, this might be necessary.
If Big EAs are not responsible with the use of their capabilities on behalf of other EAs, we will probably only reach a fraction of our capacity for doing good.