Hewes Products have always produced 70mm spirals, and they're still in the range in 3 and 5 metres. If this came about we would act as a stockist for them.

http://www.hewes.co.uk/

70mm cassettes appear regularly on ebay;

http://photography.shop.ebay.co.uk/?...tte&_sacat=625

Tanks are a different issue, the easiest option might be just using 3 gallon deep tanks.