Many thanks for the replies so far, please keep them coming.
I really do need small; so probably 11" max, (iPad size); as I also carry other electronic test gear, so I need to limit the weight and volume.
I will use it to talk to equipment via GUIs so I don't need to watch movies, look at photos or work on spreadsheets.
I also now know that I don't need a built-in physical RJ45 socket because there are many USB-RJ45 adaptors available.
I saw this tiny thing which looks quite good for my purposes, but might actually be too small, so I would need to see it in the flesh before buying. Also I have never heard of the manufacturer, so no idea about the quality.
