OP, you're asking about "scooter tours," but for some reason I'm not clear whether you really want a "tour"--with a guide who arranges routes, food, accommodation, etc.--or just a rental. In any case, the fact that you're asking whether they even exist suggests an absence of any sort of prior research.

In the FWIW department, I met a couple of Germans who'd never ridden any sort of bike before. They rented little 125 automatics with GPS included and were able to navigate through Hanoi traffic down to the coast (where I met them) with no major difficulties--not as straightforward as it might sound. There are literally hundreds of rental agencies in all corners of the country which will give good prices on scooters like this, and most will provide guides as well. Any Google search will return endless possibilities.

That means your main issue is figuring out how to eliminate most of them from consideration in order to engage a good guide and a reliable bike. Decide what you want to do, for how long, who you want to do it with, where you want to start, and what sort of bikes you want to ride; use that to narrow the field as much as possible. Check reviews, for what that's worth, since a lot of these businesses come and go or can't be trusted.

If your bike choice is unusual (I rode a rented Honda 250, for which I paid rather dearly in local terms), your decisions will almost make themselves. If more in the mainstream as it sounds, well, you might have some hard choices to make. Personally, I'd follow trustworthy advice from others who'd done what you want to do....but in order to even ask you'll first have to be more specific about the parameters above.

Hope that's helpful.

Mark