Edit: as of June 29th 2018 this answer is no longer correct as the widget has changed, as such the code below will not work as expected. Please see this post for an updated explanation of how to center the widget: Unable to center Patreon button on Wordpress site
The code posted in the previous thread was specific to their website, a more general solution that can be used across all websites is to wrap the Patreon button in a div and then center the content of that div, e.g:
<div style="text-align: center;">
<!-- Put your Patreon button code here! -->
</div>
So for you, the code is:
<div style="text-align: center;">
<a href="https://www.patreon.com/bePatron?u=11152196" data-patreon-widget-type="become-patron-button">Become a Patron!</a><script async src="https://c6.patreon.com/becomePatronButton.bundle.js"></script>
</div>
I’ll update my comment in that thread to point here so that anybody else who finds it via search gets the general solution