Why don’t you just build one that fits your work area?
As an example get a sheet of 1/2” Beach wood plywood (4x8) carefully cut it in half (4x4 or what suits your space).
Glue the two sheets together so the edges are even, use some screws along the edge and a few in the field (six screws as most) to hold the sheets together neatly on one side and make sure the screws don’t go through the other side as the other side will be your work surface. use wood filler to fill the edge gaps, sand and then seal the surface with a good epoxy sealer (you don’t want splinters!).
Get a few 2x4’s to build your legs and cross braces. Cut the 2x4’s making two boxes which are 3.5 feet square (giving you a 3” overhang around the edge). Or what you need if you use a different measure. Placing one box on the bottom of your plywood top. Making sure the edge gap is even all around mark its placement.
Now measure the center point along mid points as you’ll need to drill a hole for the carriage bolts to pass through (4 one for each side) into the top for the diameter of the bolts shaft. Start from the top drill a hole just cutting through the top 1/4” into the sheet with a drill that’s the same size of the bolts head with a socket wrench fixed to it, then use the smaller diameter for the bolt.
Now mount the legs to the now affixed box to the top in the corners from the side with one bolt from the side making sure the end it flat on the bottom side of the top, now slide the second box around the legs, here we could remove the front cross brace so you can slide your chair under. Take this removed brace back 2/3rds in for a shelf and stiffener. Add some adjustable feet if needed.