There are Aussie-made non-genuine Victa deco valves available, which
are repairable. And they're quite a bit cheaper than genuine.
They have 3 spring clips which hold the lid onto the body. Which is exactly what the early Victa valves used.
You'll have to check with Bruce, but I think this is one:
Vortex deco valve. Note that it has a right-angle, not straight, connector for the hose. But this can be swapped from your old unit, if you are careful.
The ODK Shop also stocks
Victa deco Repair Kits .
I wouldn't recommend running the deco valve without the filter, really. It does suck air in, as well as choof it out, when it's open. Edit: And in my area anyway, the open vent holes would be a mud wasp magnet, for sure.