Boot discs aren't exactly legal, so not a lot of stores will have them, but it also looks like the Breaker Pro is discontinued. I cannot find a lot of stores that carry the NTSC version either, while I have no problems finding stores that carry Swap Magic (which only works with PS2 games).
Note: If you will do a lot of swapping, also consider investing in a flip-top cover for your PS2 model. It eliminates the need for the slide tool which gets really annoying to use in the long run.
Free mcboot is good for running homebrew, and booting PS2 games, but you still need something to run PS1 games. Although I've heard that if you have a V9 or later PS2 and some method of running homebrew you can do PS1 disc swapping without the need of a boot disc. Cant remember how exactly, but I'm sure the google remembers. I have a V7 PS2, so I haven't been able to try it myself.
I do not know of mcboot, because I have mostly the original discs. For sure.
So far I know, you need for 'mcboot' (psxloader.elf), than you can play ps1 games.
The user 'djcj' swap ps1 games on a original ps1 system, it works great and he do not need any modification. But there is a other problem, we can not capture videos for NTSC ps1 games on a PAL ps1 system. I have a ps1 with modchip and NTSC games run good, but I can not capture a video file, the same problem for 'djcj'.
As the poster above you said, using a Free McBoot modded memory card with psxloader.elf (or psxlauncher.elf?) you can do this on version 9 or higher PS2s. This requires a disc swap. You need to have a swap tool (fliptop or slide key) for fat PS2s, for slims you need to keep the lid sensors pressed down.
Look around a bit on google and more in-depth info shouldn't be hard to find.