Toystory, in California the alkyd paints are now a water base formula. Not sure where the OP lives but I messed up the first can of reformulated paint I bought, adding thinner. The upside is, I used to have problems with painter-helpers thinning latex or alkyd with the opposite thinner needed, now just give them water.
I agree, store-bought spraypaint will probably come "close enough" but if you want more variety than your local hardware store carries, try a larger auto parts store where they have a HUGE selection of different paints. Bring a piece of the engine with you as a sample, and know that nobody, but nobody has a listing for that paint; you'll have to match it up best possible or pay for a custom match at an automotive finish place. Many of these will make custom spraypaint cans for you!
Don't make the paint too thick on hot parts of the engine, and let it run through at least one heat cycle and cool down before touching. I found out the hard way that the paint takes 3-d fingerprints the first time you run it.
