I'm looking to buy some bolts for my m/bike.
the type I'm looking for is hexagon but with a dome like top.
is there a correct name for them or is this m/bike manufacturers own thing?
Just bought one, it was for the clamp holding the handlebars onto the headstock on a Suzuki quad. I had to go genuine Suzuki, and it was over £3, but at least will match the other 3 bolts. Spares for old Japanese stuff is often available for a long time, could be worth trying OE suppliers.
In my experience, the bolts are made to order. There were a lot of bolts with profiled heads used by the British bike industry, ordered in their 10s if not 100s of thousands.