I bought 2 of those folding Lifetime tables approx 24" x 18". The can be adjusted to one of 3 different heights. Got mine on sale: 1 @ Costco/Sam's club and 1 @ an office supply store. Less than $30 each.
I find I don't usually use an extention table when I sew/quilt. But, I went to a local plastics company and they cut me a table top that fits perfectly around my machine. I had to make my own template so I made a pattern out of layers of freezer paper ironed together [stronger than brown paper] and then took that to them. I will take that to a retreat, but don't go as much as I'd want to. Darn.
ali