Davey Bath Pump Air Bleeds for XS and older Yellow Davey Spa Bath Pumps. Totally obsolete and no longer available.
We do not advise to use any kind of glue or epoxy to block these off. In some cases, an air bleed is absolutely necessary to allower priming of the pump, and complete emptying when unused (prevents microbe growth in pump).
If broken your best option is to replace the pump with the recommendations on this page.