Display a Block on a specific Civi contribution page using a url alias (How to)
One option is to use the solution you linked to above and then set up a friendlier redirect that forwards them to the correct internal page URL. (So you could use something like example.org/donate and when they click on it the Redirect would send them to example.org/civicrm/contribute/transact?reset=1&amp;id=8) The end result is still the default URL, but you could use the friendlier redirect in emails, campaign materials, etc.

Or, set up a webform (using Webform-CiviCRM) that takes payment/contribution. Then you can set up your own URL as usual (but can't use the default contribution form payment profiles, etc. -- you'd have to set the needed fields up in the webform).