Do you think your vet would be able to find a vet willing to come and do an ultrasound at your regular clinic? My local vet doesn't have an ultrasound but they have an ultrasound vet come and do ultrasounds all day every so often. This is how my cat Jimmy was able to get one recently. I'm sure it would be worth it for both vets in the end as they would both make money. Maybe your vet has a few other clients who would benefit from ultrasounds. Even if they could line up 3 or so, it would probably be cost effective for your vet to set it up. Just a thought.
Prayers that Kacey will stay strong and the mystery will be solved and fixed!