Currently out of stock, but if you contact Tim ( [member=68900]Systainer.Store[/member] ) , he's pretty good about getting back to people.
Other stores may also carry it, but that's the one store I know I can go to when I need to find something like that.
I wonder out loud if the profile/outline is the same as a standard T-Loc (I imagine it's pretty close), in which case you could get some T-Loc shaped Kaizen foam or the rigid pick-n-pluck of whatever thickness you're looking for and carve it to suit.