The first thing you need to know about bunk beds is how rarely can they be found and purchased. If you want to buy a bunk bed of this type, I will tell you right away that your ordinary bed will not fit. 

Even a certain company that made bunk beds could not possibly stock a rare item like this. You can now get the best twin over queen bunk bed via

Aprodz Ashmo Espresso Twin Over Queen Bunk Bed with Trundle: Home & Kitchen

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If you want to buy this type of item, you will need to buy it or do some research online. Just googling those phrases doesn't help, because there's no way anyone will do what you want unless you're in a really big city. 

If money is no object and there is a good chance not to consider how expensive this unit is, buying a specialty is definitely an option. When dealing with professional carpenters or carpenters, you need to point in the right direction. 

Personally, I would recommend a carpenter as they are much better at handling wood in terms of detail. The first thing you need to do is ask your friend to recommend a carpenter if they can. In protecting this person, you need to know that the people you hire know what they are doing. 

Then you need to send in your specifications for what you want and how big the size is with the measurements. Sending a photo of a similar design is also useful when a carpenter is thinking about what you might want. From here you can discuss and negotiate the price and how long it will take and the cost of installing a double bed with a double bed.