I've had some luck at our local ace. We're lucky and have a local bolt co that has most hard to find stuff and will sell you 1 bolt if that's all ya need.
Do y'all have a Fastenal? But they usu sell in bulk too. But maybe they can point ya in the right direction.
engine covers, low stress areas etc. (although there are some exotic grades of stainless around - to cope with crap conditions/atmosphere in various industries etc.)