My trolley is one that omnipole has recently started selling @£350
however i paid £320 from the red hat diving ppl who also sell window cleaning stuff.
Its the red 35 litre model, looks smart too
Im not to sussed with trollys but would advise you to not spend too much money upfront until you established.
It suprising how cheaply you can get wfp set up without having to spend big bucks out first, as i said up grad when you get more established