You don't even need isolation headphones (they would be nice but pretty expensive). I use closed back headphones and just turn up the volume a little bit. If your click track uses a sound almost like a sidestick or a woodblock, you can hear it over the drums.
Extreme Isolation cans or the Senn HD280 Pro's. Both are working out pretty well, I've found.
In fact, I posted here not long ago that I preferred the Extreme's over the Senn's but found out I had my headphone mix screwy and I think I like the Senn's better...