What about powder-coating just the heads?
That would be small enough, it could be done at home.
Can that be safely done in a kitchen stove, or do you have to dedicate a stove to it?
I bought a stainless "kit" for the engine side covers on my CB200 from a guy on eBay. Â
They didn't match very well, and came with a lot of hardware I don't need.
I contacted him, and he sent me a special order that was supposed to fix my omissions. Â I got all I needed plus a couple, except still no M6x55.

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Luckily there are a couple of long ones in the original kit and I should be able to cut one down.
Of course, they are silver, which is fine, as long as I keep the engine stock, but I hope to paint it black, someday.
Here is a good source for small quantities:
http://www.boltdepot.com/dimension.aspx?cc=25&cs=81&cm=19