Hi Paul,
I see you're still plugging away with that power supply.
A 'TVS' diode is a "Transient Voltage Suppression" diode and they come in a variety of current and voltage ratings.
When used to protect a typical Ham radio setup a 15 Volt, 1500 Watt is usually utilised and a quick search turns up these :-
https://www.amazon.co.uk/20-Pieces-1-5KE15CA-DO-201AD-Bidirectional/dp/B079KHNJHZ
They're often assisted by a 'crowbar protection circuit', (thyristor/zener over voltage circuit), such as used here :-
https://www.radio-workshop.co.uk/g4nsj-power-supplies-13-8-volt/
A search on the old internet will provide a plethora of similar circuitry but it's helpful to know what to type in that old search box first.
The only problem I can envisage is that your power supply from what I've gathered from you is a variable voltage type. In which case adding this additional circuitry will mean that you won't be able to adjust above 15 volts. (That might be a good thing depending on what you wanted from the power supply.) You could always switch it out depending on your use.
As ever these type of circuits aren't 100% guaranteed to protect your expensive radio but certainly better than just using a simple fuse.
I wish you well with it Paul as I know you like tinkering with this sort of stuff.
Also I hope that both you and Sarah are recovering well from your Covid bout, there certainly seems to be a lot of it going around.
Take care and all the best,
Victor