I bought this one a year or so ago:
http://uk.rs-online.com/web/search/s...duct&R=4998850
Not the cheapest, but we buy lots of stuff from RS.
They do a £20 one, which has a bleed off button too - but it doesn't give a quoted accuracy - could be worth a call to see if it has a decent tolerance.
http://uk.rs-online.com/web/search/s...duct&R=4998888