I agree, the brakes are difficult to find -- especially the levers. I found some NOS levers a while back on ebay. The Shimano name is in gold across the front with no arrow logo. The calipers (I got mine from a trade here) have the arrow logo like the derailleurs, shifters, and crank arms.

I have a bike that has the derailleurs and shifters on it in the original setup, and have seen more of those items listed on ebay. Sugino or Sakae cranksets, Dia-Compe brakes, and Shimano or Suntour derailleurs/shifters were used commonly by the manufacturers on mid-range bikes back then, so a combination of all that stuff was most popular.

Here's a photo showing the Golden Arrow levers.