Steeda has released sets of Chrome bolt caps as part of their engine dress up offerings. These caps snap over the 10mm (and 15mm) bolt heads in the engine compartment. I ordered the 10 cap set to try it out.
Here's the caps over the OEM bolt heads on the coil covers:
I used the other 6 caps to cover the bolt heads on the alternator bracket
These caps are made by Kirban Performance, and they have the same caps for 15mm bolt heads. I really need 8mm, too, but so far only UPR makes a bolt head cover for 8mm, and they are VERY pricey (they're billit alumimun).