Canadian source:
Aqua Sport has tons and tons of service kits and parts for BCD's and regulators. Are you looking to service your own or to get your favorite service tech to service them ? Maybe a part is broken and it needs replacing? Aqua Sport has WAY more parts than listed in this collection so if you need...
aquasportscuba.com
Because there are a lot of Apeks regs out there and basically only two second stage kits (Flight and everything else), the aftermarket will supply the kits no matter what happens to the parent company. What you would lose is the warranty, eventually parts other than the kits, and you might have to search a little harder to find a shop to service them.
For example, this is a current aftermarket supplier:
For Apeks gear - For Apeks gear
scubagaskets.com