Are there any tools available to convert images to WBMP?

You can find a Plug-in for Photoshop and some command line tools to convert to/from WBMP images at http://www.rcp.co.uk/distributed/Downloads.

Alternatively, if you can load or generate the image as a Java-based BufferedImage, then you can save it as a WBMP bitmap using the code snippet from the related FAQ entry on Java classes for saving to WBMP.