What's the best online service to make a simple checkout page with Stripe?

Question

I'm looking to charge one-time payment and I need a checkout page that I send to my customer. 
Ideally, I can input a percentage in the url that change my price.

Ryan Hoover · Accepted Answer

Plasso is built exactly for this, made by @drewwilson.  You can also embed Plasso into another site if helpful.

Louis de Vaumas · Answer

I found this. It covers almost all my needs, except to be able to determine the price with a trigger.

Sander Visser · Answer

I've made Checkout Page for this reason! Dynamic prices are on the roadmap as well.