Asking the companies shouldn't be impossible if its for official usage, and all those companies expect their logos to be used everywhere. So use the press and media contacts on those sites and ask for them to be provided.
Anyway:
brands of the world has most of the major logos in illustrator EPS and AI formats however they don't include how they should be used, and when displaying the "card" icons/logos themselves they're usually different from the main identity.
edit - and both mastercard and maestro make their logos readily available and with instruction... look harder before asking maybe? :P
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