Good breeders are very rare. The best
pugs (in my vast experience) come from eastonite, cariella, and jessygaff. In fact, as far as im aware, jessygaff was the leader in the pde tests in the uk.
They wont be breeding again for a while though.
Im pretty sure cariella may have some ready now, but whether they are all taken im not sure.
Be prepared to travel too. I drove 8 hours to collect one of mine. And be prepared to be interrogated. You wont have a hope of getting one of these babies if you dont pass their grilling 
And no, breathing issues isnt typical. Its called a collapsed trachia, and again, rare.
The usual issues are dry eyes which are easy to sort, and they need regular cleaning of their faces.
You also would be very unlucky to get a proper chewer. They are playful sods as pups, but wont destroy a kitchen like some breeds. Slippers however, another matter!
Where in the country are you?