The War in Vietnam, the game (BGG link: boardgamegeek.com/boardgame/247926/war-vietnam), should be a source of 50s to 70s military hardware, both “free world” and “communist bloc”. If you are looking for something more high tech, I can think of a few options:
Command Post Games (www.commandpostgames.com) makes a game called Supremacy 2020, which is a game about world combat in the coming decade. While there color palette is similar to the Superpowers game, you might find something to work with in their expansion sets for 2020, among them: “Bombers (B-2 Spirit looking things) & SLBMs” and Fighters (F-117 looking things) & Carriers", and “Glow in the Dark Mushroom” clouds, for the inevitable nuclear exchange awaiting us all in warfare in the future.
And finally, Historical Board Gaming (www.historicalboardgaming.com). While they are best known and currently oriented around WWII plastic miniatures (read - Axis & Allies expansion pieces), they are working on a series of games spanning from the 1860s to the 2050s. Once they start producing miniatures to suit the later end of that range, you will likely find something you can work with.
And that’s what I know.