How much did they want for the simple install disk without a key?
You know that you don't need to buy the Pro key again since it came with the laptop, right? You own it for life and are fully entitled to reinstall with a clean-copy Win7 Pro installer if you choose, even though manufacturers may say they don't support it in order to enforce the bloatware which now makes up most of their profit margin.
The Product Key on COA will activate after a quick robocall to MS which sorts the actual key from batch key on sticker.
MS requires makers to provide an installation DVD upon demand, so you can also call Dell to inquire. This is separate from their decision to finally quit providing Install disks, so if they refuse you can make it an issue in a thread here which MS may well see.
We aren't able to link to ISO downlloads as it encourages piracy, only suggest you borrow or find an installer of your version. Any version ISO can also be unlocked to create an all-versions installer. If you do download an ISO be sure to rightclick scan it with your AV and check its HASH and comments to make sure nothing was added.