Is there such a thing as small Evergreen plastic bolt heads that you can glue on fro drilling? Can't find any online or through the search function on this site.
Any help?

Try looking for grandt line accesories. They have a wide variety of products.

I think verlinden may do some resin ones.Try looking on the Historex website,I do not know if they post internationaly though.
www.historexagents.com

I use Hex rod and 'THE CHOPPER". There's about a Zillion bolt heads in 12 inches of rod.

Evergreen or Plastistruct Makes Six sided Rod in several Diameters. I use those and cut the bolt heads off.

I'll have to look for this hex rod. I have been using square stuff and rounding up the corners with sand paper to make it look like a bolt head.

I am thinking of making and selling small packs of glue on/stick on bolt heads. Not sure if there is enough demand across the modeling hobbies to pay off capitol expenses though.