Why don't you guys at CX wear headsets above FL150 anyway? And noise-canceling ones at that?
I spent 5 years on QF B744's using regular headsets (before noise-canceling ones were installed). It has demonstrably damaged my hearing.
QF B744's all have noise-canceling headsets now and they are being installed on other fleets. The noise level on the B744 flight deck was demonstrated to be over the safe, long-term limit wrt hearing. That's why the new headsets were installed.
That you guys are flying B744 ULH sectors without any company-provided hearing protection astounds me. That you compound the problem by removing whatever headsets you are using beggars belief.
Rather than chasing after your own earplugs/protection, you should be insisting on installation of noise-canceling headsets and insisting on using them!
Once you get used to them you'd never do anything else.