Well I found one TR inports have one that fits in the grove on top of the receiver for 11 mm dove tail but you have to drill and tap for the screws. this so someone else can make it work.
I have a tristar and went through the same bull-crap so I'll save you some trouble.
Sun optics has the dovetail to picatinny mount you're looking for. I think the part number is 7015 maybe 7025 can't remember.
Sumtoy ain't hitting on nothing.
Truglo has an adapter.
Amazon has about 4 or 5 different ones also.
The issue is once you put that on the gun plus your optic with a picatinny mount, your sight sits ridiculously high off the receiver.
Best fix..... Order a EGW base for the Ruger pc9 carbine/marlin 189. It's flat, thin, and available in different footprints to bolt your red dot straight to it. Drill and tap the receiver, screw the base down and mount your sight. It doesn't get any lower profile than this setup without customizing stuff.
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