Two failed brake boosters, can you recomend a third?

[Dead Parrot]

Sample size of 1, your results may vary, etc.

I replaced mine with one from Autozone. Don't remember the brand but its been working about a year now. Just replaced the booster as the brakes themselves were fine. Single diaphragm booster.

If yours came from a chain store, take the dead one and receipt to a different store. Sounds like they got a bad batch. Might as well swap it even if you just put the next replacement on the shelf. Might even wait a couple of months, maybe the bad ones will all get bought and warrantied.