I just buy them on Ebay. They are cheap enough that I over spec the relay by at least 50% or more. For a 17 amp kiln I get a 45 amp relay. My bigger kiln at 38 amps is running a 50 amp SSR with a heat sink and cooling fan, located remote from the kiln. Even then, you can feel pretty warm air blowing out of the enclosure.
Never paid much attention to the brand.