1) Apply for one from Disclosure Scotland : https://www.mygov.scot/basic-disclosure/
2) Apply for one from AccessNI : https://www.nidirect.gov.uk/campaigns/accessni-criminal-record-checks
We appreciate it seems strange to have to apply for this in Scotland or Northern Ireland, but these are the correct links to apply as the official UK agencies able to provide basic disclosure certificates.
It doesnt matter which one you do, they both give you the same thing.
The Disclosure and Barring Service (DBS) in England and Wales does not currently provide a basic disclosure checking service, it can only provide Standard or Enhanced checks which must be done by an employer. When working as a Supporting Artiste you will always be seen as Self Employed.
If you already have the more detailed Standard or Enhanced Disclosure Certificate from other work you do, please read this