"I want to buy that pair of Italian shoes."
I'd be carefull with that, because they both imply different meanings. I agree that in some cases both are acceptable, I would say that 意式衣服 could maybe be correct but it sounds weird. It sounds like "clothes made in the Italian way".
For example 意式咖啡 means "coffee made in the Italian way". You might also hear 美式咖啡 "coffee made in the American way" which is an Americano. However, when you say 意大利咖啡, to me that's "coffee from Italy". Not really the same as 意式咖啡.