Hi HotPinkDragon,
All the adjustable beds I’m aware of come in standard sizes and the longest would be cal king which is split into two sides which together are 72" wide and 84" long.
There is also more information in post #3 here and the adjustable bed thread it links to that can help you choose the adjustable bed that has the features you prefer and also has links to some sources that you can use to make good pricing comparisons as well.
Phoenix