T.H.
Hi M.,
You could buy one or just make one for them out of large cardboard boxes. (one for a fridge and one for a stove and oven) It's all pretend play anyway and your kitchen could very well turn into a fort or a ship or a train.
You could probably find something Little Tykes like on Craigslist for free or cheap if you don't want to make it yourself.
Good luck!
T.