As you found out, scanning takes a lot of time! And if you find a company that can do it, I'm sure it's going to cost you a small fortune.
There are actually 2 ways to "scan" a photo, and I've done both. Of course, modern technology has made scanners better and better. This method is slow and time consuming.
The other method, and professional photographers have been doing this for the last hundred years to make copied of existing photos without negatives. Simply, take a photo of the photo. I've done a lot of this also.
With advent of the "SmartPhone" and Digital Camera, taking a digital photo of an existing photo is extreamly simple, and the result are really good. It can be a bit of work to eliminate glare and a sharp focus. This is way old-school copy photography used tripods and selected lighting methods. (I've done this too, and it does work, with old school cameras (35 MM cameras), and even with digital cameras. But with Smart Phones, it's even faster and quicker.
At any rate, it might be an alternative to consider, ... photo of a photo with digital camera. I almost guarantee you, that's how a professional scanner service will do it. It's so much faster than a flat top scanner, once you've got the space and equipment set up, and then it's just a matter of repeat, repeat, repeat taking photos of photos.