The bolts are highly standardized and often come with the bottom brackets. You can buy either the newer cap screw (allen) style for use with a hex key, or the more traditional 14mm bolt which uses the tool you already own.
Before buying, check if they're included with the bottom bracket and if not you can pick up a pair anywhere. BTW- if you can't find them cheap, I have a bunch of the 14mm type and can sell you a pair for $4.50 including postage.
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