I have a rive and a trolley system as well to go with it. Personally i cant fault the system myself and pack tonnes of gear on to it every week and never had a problem with it. However i know a couple of people who have and being in the situation where you have got a box but no trolley then i would say that a penrose xxl barrow would be your best best as it doubles up as a large platform also and is about £30 cheaper than the rive trolley. Best place to get one would have to be the penrose direct website as you can pick one up including delivery for £95 (
Penrose Direct - Online Angling Equipment Shop)