Not sure you'll find one the same size, but good luck hunting. I think there have been several threads from folks wondering how to deal with the bezel since the new microwave isn't the same size as the old one.
If it's brand new, I'd go back to the dealer or the microwave manufacturer for a new one under warranty.
1988 Coleman Sequoia - popup (1987-2009) - outlasted 3 Dodge Grand Caravans!
2012 Roo19 - hybrid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado 1500 Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10