Where to find a Dressage/ Eventing Schoolmaster for Lease?

I’ve just started college and as much as I’m loving the IHSA Hunter competitions (got my first blue ribbon for Equitation this weekend! Whoo!), my true interest is in Eventing. I only have about 6 months of Dressage training under my belt and I’ve only started to jump on hunters so I have a lot to learn but I’m eager to get started and try my hand at some real competition. I’ve been looking around for a horse to half-lease or shareboard over breaks from school - a horse I could lesson on and practice up to at least third level dressage, improve my jumping skill and maybe take to some lower level or schooling shows over the summer… but I’m having a hard time finding horses. Where should I try looking? Any suggestions on barns or trainers I might talk to? I’m in the Denver/Boulder area of Colorado.