Sorry to hear that they give you blisters

I have non-patent cage flats, and they gave me pain in the beginning too, I had to stick in cushioning in the spots that rub and caused blisters. I used cushioning by Dr Scholls, I forgot what it's called but it looks like the pic below. It's a tape of cushioning that you can cut to size:
View attachment 3306838
Foot petals have a product called 'Pressure Pointz', which are tiny versions of the inserts that you can stick to problematic spots.
Best of luck in breaking-in your pair, don't lose hope! [emoji173]️