Is there a module that provides payment processing but not a shopping cart? I am building a website that allows users to "upgrade" their content. The user can choose a "premium" listing and once paid for their node will appear higher in a list of nodes.

I'm looking for a module that can do this, or a module that can at least provide the payment page so that I could customise the node editing process and direct them to this page, take their payment then update the node.

I know something like Ubercart can provide the payment processing but it has a very set payment checkout process that is more oriented to a shopping cart checkout process and would take a lot of time to customise for what I want.

Any recommendations on how to do this?

Im running Drupal 7.
Have you tried some of those ?


lm_paypal: 


  This module provides an interface to PayPal using Instant Payment
  Notifications (IPN). It currently supports paid memberships
  (subscriptions), donations (tip jar) and paid adverts (classified
  ads).

Payment API: this one need a specific module for the payment platform


  This module can be used by other modules to collect and track payments. Through this API, any module can provide a payment form and payments can be handled and tracked centrally.

How to build a paid membership site with Drupal 7 (paid module)