A little while ago I picked up a Tandy 102 portable computer. Although not directly related to Atari, the Tandy was regarded as the premier portable computer in the 80s and was perhaps the first true notebook computer. They often were used in conjunction with another computer, almost as a peripheral of sorts.
The Tandy 102 is actually the revised version of the Tandy TRS-80 Model 100, the first computer in this style. Release in 1983, the Tandy 100 sold for $1100 (about $3300 in 2023) and came with 8K RAM. You can get a pretty powerful MacBook Pro for that price today!