Could anyone help me locate parts for a Lennox G12Q3-137?

My furnace filter is a disposable type, held in place by a brick (yes, a brick) and a cheap piece of metal the last guy screwed in to the thing.

Previous owner was cheap as hell, which is why it's set up like this. I'm thinking that Lennox probably doesn't supply a brick when you buy the furnace. Is there a name for the piece that should be on the bottom of the furnace to hold the filter in place? Or, should this furnace be using re-usable filters? I saw a lot of references in my searching that seems to indicate that this thing might not be built to use disposable ones, so I'm wondering if the other owner damaged the washable one and was too cheap to get the correct replacement. The box of replacements he left look like the cheapest filters you could possibly buy which is right in-line with the way he fixed stuff.

There's a metal bracket running along the top of the hole (intake?) where the ductwork comes in to the furnace, and while there seem to be some holes on the bottom for bolts or a spring or similar, there's nothing attached to the bottom of the intake, just the brick. The filter size is 20x25x1.

submitted by /u/G19Gen3
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