I made this solar filter to fit my C8, since traded in. Used only a few times. It uses 8" needlepoint rings which are stapled together to hold the Baader visual film. The ring is a perfect fit for the C8 and allows you to mount it snugly. Small extra piece of film to mount on your finder with an elastic band.
Provides excellent performance. Note, the film is supposed to be mounted without stretching, hence the billowy look.
$40 plus actual shipping costs.