SAAS landing page with pre order

I have an idea for a SAAS solution which is in an extreme niche market. I know exactly how man possible customers there are, a little over 300.

I already wasted to much time (2 months fulltime) working on an MVP and after showing it to one of the possible customers I realized I should have talked to them before even starting. He liked the idea but would have shifted the main goal to something different. To realize what he want's I would need to put in another 2-3 months which I don't have.

I learned a lot :)

So now I'm looking in providing something very basic which I can charge a couple hundred $ a year for each customer. And I cannot waste more time/money so I'm thinking about a landing page with pre-orders for the service which will be ready by 1st of January 2019.

I there any landing page creator out there with pre orders built in?