Foster is best known in the US for their "Fostex" brand.
Foster, Automatic Radio, and others in Asia (often, but not exclusively, Japan) made electronics for companies like Radio Shack and Lafayette (e.g.) in the 1960s and 1970s.
Details would generally be scarce, because the electronics were often "proprietary" products for the US brands who contracted for them.
Sometimes, the 'store brand' electronics were simply rebranded (or subtly different) versions of "big name" Asian consumer brands. E.g., many Radio Shack cassette decks (maybe 8-track deck, too??) were Hitachi-made; Lafayette sold more than a few rebranded (or "OEM" version) Kenwood (Trio, in those days, in Japan) receivers; Allied sold Pioneer OEM products in the 1960s up through their (brief) assimilation by Tandy Corp. ca. 1971. Many of EJ Korvettes' 1960s "XAM" branded products were made by harman/kardon. Much of JC Penney's "MCS" equipment was made by Panasonic (more specifically, the Panasonic brand's owner, Matsushita... which is now itself known as "Panasonic").
There were some interesting exceptions -- e.g., the late 1970s Lafayette receivers made by the same mfgr as the slightly exotic (and short-lived) "Setton" brand; the LRE and Setton products are virtually, but not exactly, identical.
Later, as the consumer electronics market was shifting seismically, it became common to see 'store brand' components that were simply rebadged Pioneer, Kenwood, Panasonic/Technics, etc. E.g., by the 1990s, much of Radio Shack's "Optimus" branded hifi electronic equipment was Pioneer, sporting only a different name badge & model number.
