Welcome to the Forum Drakhorn!
At the time, I could not find a suitable 1/2 time oven replacement due to the required venting and clearance, however - Keystone now uses a Sylvania 1/2 time oven that fits in that space. I do not know the details but the Dealer should have the info. I could not find the actual oven on the web page, so it may be a proprietary model for RVs.
We replaced our Apollo with the standard Microwave. Our Apollo NEVER
cooked or heated anything, as it broke first time out. We figured we could never miss what we never had the chance to use.
We opted for the Amana Radarange in black, primairily because it had a ducted ventilation system as part of an optional trim kit, and because it had a very sexy chime. No other reasons than that, as there are plenty out there to choose from. The Micro is 1.4 cf available at Sears for $139 and the trim kit was $69. I did have to cut about 3/8" off the top and bottom of the opening to get the trim to fit, and I secured the microwave to the base with sheet metal screws, as it just was a gravity mount.