Scythe sells fans that come in a bracket (Newegg, etc. carry them) or you could mod three bay fillter plates to hold a fan. Or you could look on CM's site and see if they offer such a thing as an optional accy. The drawbacks to the Kama Bay are cost and very little air flow - they are about the quietest 12cm fans - now you know "the rest of the story"...
Personally, I'd take advantage of the nexfan.com offer of B2GO on the Yate Loons and use the 'cheapship' code for $5. flat shipping. Put one in place of the one on your 4-in-3 cage (as that doesn't push much air either (I know I had one) and mod 3 of the bay fillers to hold one and keep one in the closet for a replacement or replace the rear fan with one. If you can't deal with the orange,
http://www.jab-tech.com has black one w/ white blades at a decent price if you can buy something else you need there too. I can't see paying more for shipping than you do for the item...
I think all the fans that come with the stacker are the same model as the one on the HDD cage - pretty quiet but don't move much air. I'd even suggest putting a Sanyo Denki in the rear (the one that PetrasTechShop.com sells for $12.) but you will need a fan controller for it as it's a bit feisty at full speed since it can move over 100CFM. The rear fan is the more important one for keeping the case cool. Putting the front fans (incl. the one on the HDD cage) as low as possible on the front will get more work out of the intake air.
If you decide to consider heftier fans with a fan controller, click on the link in my sig.
.bh.