Where can I find celebrity photos for commercial use?
Every commercial-use photograph website I've looked at (flickr, shutterstock, getty images, etc) have plenty of pictures of celebrities, but literally none of them have model releases, so they can't be used for commercial purposes.
Does anyone know of a source that provides celebrity photos with model releases?
A celebrity is a brand.
That brand is marketed to generate revenue, by using that brand to endorse products or services.
By providing royalty-free, commercial use, photography you are asking that a celebrity grant the right to use their likeness to promote anything anyone wants. They don't do that for very good reasons. Suppose the celebrity has publicly taken a hard stance on animal cruelty. Do you really think they'd want any animal testing facility to be able to buy a stock image of them and use it in their advertising??? Of course not. So, they protect their brand by not distributing any royalty-free commercial use images.
Since the brand is a person, celebrities customarily want to know what is being sold before they agree to their likeness being used. This also often comes with a fee. A fee customarily much higher than any royalty-free stock service charges.
If you wish to use a celebrity likeness to endorse a product or service, you need to research and find the agency managing the celebrity and then contact them to negotiate an endorsement deal.
You won't find "royalty-free commercial use images" of celebrities anywhere. All commercial use celebrity images would be what is referred to as rights managed images, not royalty-free.