I have had a super Microwave, by Hitachi, for nearly 25 years now. It big inside and is easy to operate. Its also has a Halogen grill. I can honestly say that I have never used this facility more than 10 times in 25 years !
Its not very efficient and makes a nasty mess on the roof of the inside of the Microwave, which is a devil to clean.
However, you can get genuine "combination" Microwave ovens, which have an electric element instead of the halogen thingy, but I have never used one, so can't really comment. But I would imagine that they are just as awkward to clean as the halogen one.
But I will stick my head out here and suggest that they will probably never be as good as the grill on your cooker !
By the way, I have heard nothing but praise for those Coleman Grill things, and if I had more room in my kitchen, I might treat myself. Everybody says that they are easy to clean and produce good healthy grilled foods.
I hope all this has been of some help Rtaxron !