Lots of great advice here.
Yes, you can do it without riding a schoolmaster. Your horse appears to have some natural ability, and you have good instruction.
However, I wouldn’t completely give up on trying to find an opportunity to ride a schoolmaster because it is a wonderful addition to your education.
I’d continue your search, but change the ask somewhat. Look for an instructor or facility that will let you come for a weekend or long weekend and take twice a day lessons on their schoolmasters. Have someone take video of you and your current horse working to include with your request and have you current instructor write a recommendation. Explain that you want to experience the correct movement on a made horse before attempting on yours. Yes, it will still be expensive, but it will be a one time expense, not an an ongoing expense.
Focus on the level directly above where you’re working with your horse and anything you feel that you’re struggling with. It it’s an upper level horse or horses, go ahead and play with some advanced movements, but mostly focus on what’s next in the training process for you and your horse.
Best of luck, and hope you find something.