PSE 11 upgrade

I have been running PSE version 11 for many years and am still quite happy it meets my needs. BUT I run on MACOS which changed from 32 bit architecture to 64 bit a few years ago and PSE11 is 32 bit.

This is now the only application which prevents me upgrading to enjoy later MAC 64 bit OS.

PSE upgrades are not cheap, but can anyone advise how to upgrade a basic PSE and what options I might have version and/or cost wise.  I am only an occasional amateur user.

All ideas welcomed.