Splitting orders by product

My client has a particular product in his store that can't be shipped with any other item in his store.

When someone orders this product and other items simultaneously, the main product is shipped elsewhere from a warehouse while the remaining products are shipped together in the one order.

I've found a module for creating split orders, but what we'd ideally like to be able to do is to prevent checkout if the main product + other items are in the cart, forcing users to checkout separately.

We completely understand the aggravation this may cause, but it's something we think will work anyway.

Has anyone come across a module for this?