I'm not sure my idea is practical or would even work in your fingerjoint situation, but here goes.
My router fence is a 4"X4" square aluminum tube with a 8" long by 4" high opening in the side at the router bit location. This opening is for replaceable plastic inserts that your bit cuts through. Sorta like a zero clearance insert in the table saw. On one end of the fence/tube is a vacuum hose connector. The other end is closed.
When I do table work where the bit is outside the fence, I remove the plastic insert and allow the vacuum to pull dust into the tube. It isn't 100%, but I collect quite a bit this way.
I'm thinking that, in your situation, you might find a similar square tube of plastic, or build one of 1/4" ply or MDF. Building it would allow for different sizes, too. Of course, the tube could terminate a ways beyond the router bit, where mine spans the table. Or, you could use it as a fence. You could even make the opening, at the source of the dust, adjustable with a sliding door.
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