As of February 2015, GE does not make a microwave that is specifically designed to be mounted under a cabinet. However, some of their compact and subcompact countertop microwave models can be mounted underneath cabinets with a mounting kit.
The WX4-A109 under cabinet mounting kit is made by GE and can be attached to at least three of their countertop microwave models: the Profile Series 1.1, the Profile Spacemaker II and the 0.7 cubic foot capacity countertop microwave. It may be possible to mount other types of GE compact and subcompact microwaves that are no longer in production, and their website allows owners to search by model number to see if their model will work with the mounting kit. The search function can be found at the GE Filters, Parts and Accessories website.
The Profile Spacemaker II is an 800 watt, 1.0 cubic foot capacity microwave oven. Unfortunately, it is no longer produced by GE. The Profile Series 1.1 is an 800 watt microwave with a capacity of 1.1 cubic feet. It is currently in production and comes in a black, white or stainless steel finish. The 0.7 cubic foot capacity model also comes in this same range of finishes.