The Infinity do a basic hauler bag with 3 boxes in which is very reasonably priced, then Team Integy also do a similar bag but with 4 smaller boxes in it. Ive had both, both lasted around 2 years as the card can only be bent so many times before it falls apart
then when the duck tape gives up too, time for a new one.
How about a wheelie box from B&Q, I have one and it is excellent. A lot of the racers in the USA have them, not as common here, I know a few have them such as Cree. They are just a big plastic box which is extremely well made and has wheels. The one I am talking about might be too big, but its worth a look (will have mine at Kiddy with me). But ofcause there are always smaller versions - not sure if they will have wheels etc. i think its a better option than buying a branded bag as you'll pay a premium for that, rather than for quality... (don't get me wrong, the TM bags are ace)