I think you mean what is/was called whalehide pots....
We have couple of people using these type of pots, though there is new version of them now, the old 'whale hide' ones are not existing no more ( I think), our members did accepted happily the new replacement version that actually is said being better!
We got ours from growell-direct.. though is not in their general catalogue and you might need to give them a ring...and we had to buy them in bulk too(couple of hundred at the time I think), they were not available in small quantities. The new version is called 'culture pots'.
Edit to add...found this page for you and you can follow up to find the stockist from here too..
http://www.william-sinclair.co.uk/gardening/products/pots_and_matsFailing that..we could do some arrangements to get some from our allotments shop and get them sent for you...