I use an open top fabric box carried by one of those fold up sack trucks which the firm supplied with my van. This is handy as it just hangs up in the back of the van when not in use. It can also be used to transport other gear, such as step jack, boxes of parts, oil drums etc. Not sure what make it is, but it's lightweight and sturdy, (Rated to carry 90kg) and has lasted 3 years so far. Only has plastic wheels, but that's not been a problem, it will go up steps. You might be able to use your existing toolbox with it, depending on how big it is. Some would say I don't carry that many tools and have an easy life (Hi Shuggs!) but my everyday kit weighs 30kg and it works fine with that.