Hi Whistler and welcome to the fun!
In answer to your questions above, I, for one, just use the breaker for testing, then once fixed go back to a tube fuses - more cost effective, and much neater.
The breaker is really useful - as per others on that post, I did not solder a fuse to it, just use crocodile clip leads, like: https://www.amazon.com/Goupchn-Alligator-Electrical-Double-Crocodile/dp/B08C5BFNNJ/ref=sr_1_11
Those leads are super useful for other troubleshooting too.
And yes, pbresource.com is the go to parts shop - at least for many of us here.