It is not possible to limit a Receivers query to only specific Participants based on the Registration Type within a mailing.  There are filters such as Amount Raised, Registration Date, etc., but Registration Type is not an available filter.

However, you can create a contact list of the participants and add it to the mailing's receiver query:
Step 1: Run a particpant report in the thon event
How to report on Kintera Thon registration fees/types and descriptions

  • Add the Supporter ID column in the report results
  • Export the report as a CSV
Step 2: Import the contacts with a special flag
How to import or update individual contacts
  • Choose Allow update records using Kintera supporter id
Step 3: Add the contacts to a contact list
How to create a contact list in Sphere
  • Choose Add Contacts by Query
Step 4: Add the contact list to the mailing receiver query
How to add a contact list to an email receiver query