Refrigerator defective

Hello dear camper community! My Elektrolux RM 200 has given up its mind. It does not work with electricity or with gas. Is there possibly the cooling liquid evaporated? Is there a repair (38 years old), or is there a cheap replacement for this type? The newer models have quite different dimensions,unfortunately. Who had the same problem before,and how was it solved? MfG tabbertklaus