Depending upon the brand, chambers are certainly replaceable. If you have a soft chamber, they usually have cracks, but if the break is near the top of the chamber, it is possible to burn through the base or ruin the upper part of the boiler.

Call the manufacturer of the boiler for local parts sourcing. Most every boiler using a combustion chamber has replacement kits. I've had mine replaced once. Not a big deal. Got the replacement through a local hardware store that dealt with the boiler company's parts. Search combustion chamber+"your brand" using search engine. I see Weil McClain kits going for &$50-70 bucks. These get cracks in them from age, but more so from rookie technicians that hit the pot with their flush brushes during cleaning.