Where can I buy some dilute acetic acid from?

I've bought some Peelaway from the internet
to remove paint from plaster mouldings,
it's made of Sodium Hydroxide, an alkali
and it says i need dilute acetic acid to wash down afterwards.
The kit even includes Litmus paper to check its been neutralised!

I think its vinegar but that would stain the plasterwork wouldnt it?

[g]