older cat with Hyperthyroid disease

Any suggestions on alternative methods to help my cat. He is 10 years old. My vet won't give a prescription unless I spend alot of money on numerous tests. Has the typical symptoms of the disease - vomiting, diahrea, drinks a lot of water, eats well, over active (running around), hyper and restless, losing weight rapidly. Vet says he has an accelerated heart rate and possible heart murmur. Sometimes he has a hard time with breathing. Cannot buy methimazole or tapazole on the internet without a prescription.