wrote:

I want to do some anodising, and I am trying to locate a source of
sulphuric acid.

Chromic acid used to be the way to do it, sadly the bloody
environmentalists whinge about the toxicity.

You need approximately 15% sulphuric acid (i.e. dilute "battery acid"
50:50 with deionised water). Battery acid i bulk is quite cheap, about
£1 per litre. Your problem is that it's a strong acid and expensive to
transport which bumps up the price for small quantities.

Don't even begin to think of using old battery acid. The concentration
varies and it is contaminated with lead and other gunk which will mess
up your attempts to anodise. You should be able to get new battery acid
at any half-way decent car parts store.

If you haven't already seen it, this site is good.

http://bryanpryor.com/anodizing.php