My two cents:
http://www.baumbat.com/clearance-baum-bats.html
You can pick-up a 33/32 Baum bat for $189. Yes it's a bit pricey...but it will NEVER break. GHHS jr has been using the same 33/30 (cages, practices, and games) for 3 years (literally thousands upon thousands of swings) now and used a 32/29 for the prior year (outgrew it and re-sold it).
It's as close to an indestructible bat as you'll find. The owner of MacDougall bats also posts on here and might make a heavier cage bat, but I'm not sure. Maybe he'll weigh in for you.
Thanks GHHS. I haven't been on here in a while and just stopped by. Update on the Baum bat is that they are now $219. Fine for cage but know that they swing (Moment of Inertia) about the same as a wood bat that is about 1" shorter. A Baum 33", -1 would feel about the same as a 32" -1. This is because there is no wood in them and they are made to swing "lighter".
To be truthful, I hate seeing my bats just used as cage bats although many have. They are super durable but they also outperform any "pro maple" or Baum or DeMarini on the field. This is customers opinions, not mine. Also proven at the Sports Science Labs at Wash. State U. Charts on site. Baum is good choice for cage but go 1" longer to get the effect you are looking for.