you'll be lucky to find something which will grow to exactly the size of your trellis then just stop.
https://www.taylorsclematis.co.uk/clematis-avalanche.htmlI've got my eye on that one.https://www.taylorsclematis.co.uk/clematis-jingle-bells.htmland this one too.
This is my Avalanche in full bloom, it has been in about 4 years and is next to a pyracantha which flowers just after the clematis. Avalanche has got a bit over exuberant and when the flowers have finished I will give it a haircut, the foliage tends to look a bit scruffy when it has flowered . I believe the growth information was 1m wide x 2m tall and it has certainly exceeded that. It is a great plant for early spring and I love it.
I do like that, looks full and thick.