I don’t know the location of the pump on your model, or the model of your Vacuflush…but here are a few resources for parts to get you started…Interestingly, even places like Home Depot carry some parts, such as duckbill valves.
https://ardemco.com/vacuflush-toilet-parts-foot-flush-toilets/
https://www.rvpartscountry.com/RVToilets
https://www.environmentalmarine.com/k-506-rebuild-kit-1/