To change the steerer tube you'd have to outlay for a whole fork
An angled up stem would be your cheapest solution, but IMO you lose something "the Look", maybe if it has the same profile as the top tube, that's if it slopes, similar angle... and if it's short it would look OK & a shorter stem would give you more of an upright sitting position too.
What year model is your Cannondale?
Last edited by le mans; 10-09-19 at 11:00 AM.