Wasn't there a thread on here a while back about someone making their own turtle box they had a link to the instructions and stuff. I think they did it for like 250 or 350 bucks.
I haven't looked into the turtle box that much but I've been using these Fugoo speakers for several years now and for the price and battery life, I don't see how they can be beat. Gets very loud and the battery last well over a full day. You can pair them together too, which I do frequently in the shop and it's pretty awesome.