Valve cover bolt thread pitch and diameter??

Just take one off and take it to either an auto parts store or (better yet) a hardware store that carries Metric (proforably stainless steel) bolts. Some Ace hardware stores carry these items. Lowes does too, but you have to buy them by the bag.

I wouldn't buy nuts or bolts from Lowe's or Home Depot, even for a valve cover, because I've gotten the worst quality from them, and I mean carbon bubbles and even no threads. I think the nuts are all lower strength steel.

OTOH all the metric bolts I've bought from Ace, True Value, and other real hardware stores have all been really high quality, roughly equivalent to SAE grade 5 or 8. And all the stainless steel nuts and bolts have so much chrome in them that they're nonmagnetic.