This is going to be a bit long as I am going through the same thing right now.
If you have regular blade style keys, then you might be able to pick them yourself or have a locksmith come out and pick them for you. If you're certain that the keys are locked in it, that would be the easiest thing to do. If you lost the keys then you have the cost of picking/drilling out the old locks and hopping that he has replacement locks. I was tempted to drill out my locks and just buy new ones, but replacing the lower one (see below) was too fraught with potential incompatibility issues (plus my drill and bits were locked in the box).
I've got a 42" Steeltek. Lost the keys. The upper and lower are keyed differently, but they appear to have the same key code. These are the round circular type keys. I called a few locksmiths and they couldn't find Steeltek tool boxes to cross reference the code(s) to.
My upper lock is a 1/4 turn to lock/unlock. The lower lock is also a 1/4 turn, but the cylinder assembly then strokes in/out.
First the easy one on the bottom box. Search YouTube for "bic lock pick" or "bike lock pick". I didn't believe it at first, but after a few minutes of jamming the barrel of a bic pen into the lock, them damned thing opened!
I couldn't jimmy the upper one utilizing the same method. I could see the catch cam if I picked up the lid a bit so I did what any man would do, I started hitting it with a flat bar. It eventually popped open. I don't think that I hurt the lock, but I'm not certain.
Now with both boxes open it was pretty easy to get the lock assemblies out. No problem finding a replacement lock assembly for the upper box (Lowes, HD, Woodcrafters, etc) in a regular blade style key. No luck of any kind on the lower lock assembly with the extend/retracting cylinder assembly with either a tubular or blade style key.
I found a locksmith with a storefront. Called them up and they said that they could look up the code or make a key from scratch. Took the locks in on Sat. No go on the code look up. So they're going to cut keys from scratch. They'll be ready next Sat. $25 to make each key and then $15 for each duplicate. So $80 for two sets of keys. Kind of crazy b/c I only paid $300 for the tool boxes off of CL.
There is a specialized tubular lock pick tool. You can see them at work on YouTube. They're about $80 + shipping.
Good luck!