I haven't had much luck in the past with any kind of tray other than the massive wheelchair ones which trap you in the chair (functional and inclusive
).
But I came home to a surprise package today (from a good friend), containing a bag/lap tray which moulds to you on one side, you can strap it round you and has a surface on the top so you can just stick velcroed items down without putting the loop side on first. As it straps around the waist, it seems to have more tolerance to my involuntary movement than standard lap trays.
I am pleasantly surprised (colour's not bad either), and thought it was worth posting here in case anyone else was interested.