Welding Tips and Tricks

Hi.
Questions. So many questions.
But first, Story goes : I have the chance to buy a used Satellite hood (~$18). I'm told it has a dark spot in the lens. Waiting till after this bunny egg holiday weekend to get photos. But in the meantime i'm scheming schemes of what i might do to use this helmet if it's in good condition beside the lens. Buying a new filter cartridge from Optrel is out of the question. They price themselves out of that. Surely on purpose.
I'm pondering fitting some other filter into it. Maybe even a static / passive glass. Gives me a way to get quality head gear; to test whether i like optrel hoods; etc, without the standard price tag. (jobless poor african beginner). BUT i don't know much about the inside of an Optrel hood.
What size is the cartridge? - optrel site doesn't say.
Do you know which other filters are that same size? Lincoln? Miller? Cheap Chinese Knockoff?
Anyone tried this?
How does the cartridge get retained? - i can't find good photos / video of this online.
Do these hoods have a common failure mode that i should ask the seller about?
Any info or ideas would be appreciated.
Peas.

I wouldn't even bother trying to go this route, you may get lucky and find something that fits but I doubt you will, even if it does fit "pretty good" or "good enough" if there is even the sligtest gap somewhere and UV goes around the lens, you will be paying a lot more than you ever would for a helmet.

Why not get a cheap auto dark for a backup or craigslist helmet. Just a thought.