Where can I purchase a iPhone 5 case that attaches to a tool belt?

It needs to be big enough to hold the iPhone 5 with a standard rubber case on. Most of the cases for whatever reason are only big enough to hold the iPhone with no case on.

Most of the cases are only big enough for a 'naked' iphone because most of the users want a perfect match. But they do make some bigger ones. Check here:

This case is 12.5 x 7.34 x 1.2 cm, while iPhone 5 is 12.38 × 5.86 × 0.76 cm. It should be big enough for an iphone 5 with a slim case.
http://www.tvc-mall.com/details/Horizontal-Belt-Clip-PU-Leather-Holster-Pouch-Case-for-iPhone-5-I5-2181/

If you're not sure about that one, I'm sure this one's big enough. It's 17.3 x 9.2 x 1.4 cm, big enough even for galaxy note 3.
http://www.tvc-mall.com/details/Capdase-Belt-Clip-Holster-Pouch-Case-for-Samsung-Note-3-2-S4-S3-LG-G2-iPhone-5s-5c-Size-173-x-92-x-14mm-MSP-288/