I would pay money for a wallet-sized booklet with instructions to the cashier on declining DCC in multiple countries and languages.
No use. In some countries (e.g. China), you just can't. Not even with the most helpful of cashiers and staff. The terminal is set to DCC even if you take it down to its components.
You don't need a Berlitz Phrasebook on "Please charge me in your local currency", you need a chip reprogramming handbook. And a solder iron.