Hi @Stephen_Donahue - I’m afraid that the way you’re currently retrieving that data is the only way via the API to list all Balance funding-sources with positive balances. There isn’t an endpoint that returns all Balance funding-sources, or the ones with positive balances.
Having said that, if you find that having such functionality in the API would be beneficial, please feel free to let us know! I’d be happy to pass this along as feedback for our Product team!