VGA Conversion Card for Expression 1 and MicroVision
The Expression (1) and MicroVision family consoles use CGA format monitors. While the connector may look similar, it is incompatible with VGA displays. Inputs on CGA-compatible monitors may be labeled "RGB." The CGA format is completely obsolete, and there are no display manufacturers who currently implement it into their products.
You may be able to find used CGA monitors online, but exercise caution--CRT monitors are notoriously difficult to ship safely and you may wind up with an expensive, heavy, broken display that will be difficult to properly dispose of. We recommend searching for monitors locally.
Converters for obsolete video formats are often used by retro computer and video arcade enthusiasts. While ETC cannot provide support for any 3rd party equipment and has not tested any for use with early consoles, one such converter is the MCE2HDMI, which can be found here.