What are the ways by which an alchemist can access the alchemical bomb crit specialisation?

See the title. What methods are open to an alchemist that allow them to gain access to the alchemical bomb’s critical specialisation effect (increasing the splash radius to 10ft)?

This includes ancestry choice, etc… So far the only thing I’ve found is an Orc or Half-Orc taking the Hold Mark feat. Is there something I’ve missed within the class itself that grants this benefit?