I'm sure that was a Maxum item, not the stereo manufacturer's. I have the identical cover. If you're at all handy you might could fabricate one out of plexiglass. Not sure how you would hinge it but I'd bet it could be done. Good luck!
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1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL SOLD
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
2012 South Bay Pontoon