Yes, [member=58857]Crazyraceguy[/member] the PSB420 has the manual lock built in.
[member=61125]dalep[/member] , the reason I pointed to that thread is because it sounded like you were looking to purchase this clip from someone and I didn't know if you had read that thread. If you want to purchase the clip, the classifieds would be the best place to post, as it's much more direct ask for the purchase of an item.
If you want an alternative, honestly, the plastic "lock" is about the same size as a large paper clip or a popsicle stick and there's nothing special (bluetooth, NFC, hall effect, etc) about it. One could likely find something in the scrap bin to wedge in place to hold the power trigger in the "engaged" position, or 3D print something that fits and works the same as the OEM piece.
Also, the reason that the CMS was discontinued is the same reason you can't find that clip included in the kit any longer and you can't buy it from Festool.
edit: The butt end of the thick gold blades is pretty much the perfect size to wedge in that opening. If you have a dulled blade of that size, you could hack off the blade end and use the T end as your trigger lock. A wrap of blue tape would help reduce the slickness and hold it in place as well.