I bought a set of these from Spa in Harrogate by mail order a couple of weeks back;
http://www.spacycles.co.uk/products.php ... 2s173p1931
They also do single and triple chainset packs. Not only are the bolts stainless steel and thus good value at a fiver a set, but the actual engineering is brilliant - each half of the bolt is machined with an allen bolt fitting, meaning to install them you just need a pair of allen keys to tighten everything up, rather than either (1) needing to source one of those special wrenches with a fitting for slotted chainring bolt backs or (2) not bothering with (1) and your chainrings coming loose.
No connection with either the manufacturer or the retailer other than as a chuffed-to-bits-customer. They also do some nice self-extracting square-taper crank bolts for a tenner a pair:
http://www.spacycles.co.uk/products.php ... 2s173p1273
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