Just remembered seeing this case, which looks nice:

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I use a 'Stanley' Contractor's rolling toolbox and the rollon when I transport and perform and the whole house when it's stored back at home!
I have also seen a chap who uses three stacking crates with lids which were about 18 * 30 inches and were about 20 inches deep. These had roller feet on the bottom one (not much use in the middle really) and some black material which was stuck, using velcro, to make it look like a table. The finishing touch was a semi-hard foam insert which raised the table surface out of the dip in the lid and gave a good close-up mat finish to the job.
Reckon that would cost you about £25 - 30.
V