Hi, Robin:
Are you eating something with the PTU, or are you taking it on an empty stomach? Maybe eating something, or drinking a glass of milk with it, would eliminate the indigestion problem. It may be worth a try.
And try calling a local pharmacist about the relative costs of Tapazole and PTU. But make sure you get a “monthly” cost, not a pill cost. Since you only take Tapazole once a day (I think) typically, you might be buying fewer pills.
Take care,
Bobbi