The Expression (1) and MicroVision family consoles use CGA format monitors. CGA monitors are not compatible with current monitor standards. Unfortunately, the console cannot be upgraded to current video standards. You will also not be able to buy a CGA monitor off-the-shelf at your local electronics retailer.
You may be able to find used CGA monitors on-line at sites such as ebay.
In addition an internet search for "CGA to VGA" converter will return quite a few possibilities. As ETC has not tested any CGA to VGA converters we cannot not make any recommendations for a specific product.
The device from Editware that was previously listed on this page appears to be no longer in production.