Tim
Are you looking for a "Studio Easel", usually made of mahogany or oak,
large and heavy to support large canvases. A "Sketching or Field Easel"
that is fairly light and easily carried or a "Sketchbox-Easel" that
provides a box for paints, stores canvas or canvas boards and is
usually part of the easel.
I built my own studio easel (2, in fact) several years ago and I may
still have the plans in the archives. My field easel is a cheapy
aluminum photo tripod fitted with a shelf and a bracket to hold the top
of the canvas. A long time ago wife #1 gave me a Grumbacher
sketchbox-easel costing over $100 that was more of a PIA than it was
worth. They're impractical if you work larger than 24" and very heavy
when loaded with tubes and bottles.
I recall many easel designs available in some Sunset books and many of
the available painting instruction books so it may be best to check the
library. In any case, nothing is sacred so you can dimension it to
suit the artist and the work.
Joel