Here's a heads up on some very cheap converter kits to turn a regular monitor into a touchscreen.
http://search.ebay.co.uk/_W0QQsassZcoomb77QQhtZ-1There are approx 20 on sale in a few different sizes (10, 18.4 and 21 inch) and so far there are no bids on any of them with under 3 days to go.
Here is the companies spec sheet.
http://www.zytronic.co.uk/zytouch_spec.htmThey appear to work via the serial port and are for external machines so they will be rugged. If you can get one at