Milliput ( or any two part epoxy paste ) should do it i think.
I remember someone saying to me that these products were first used
to clog
holes in all kinds of industrial pipes ( including highly heating
ones ) before being
used in all kinds of things , like scratch building
www.gremlins.com if you wonder what it is ).
May be standard ( liquid) epoxy could do it also....
Pierre Tremblay