Try the guys in Nags Head, Marine Electronics of Outer Banks.
i got a really good used garmin radar unit from them last year and price was good too. They had a number of them then and prob have something that might work.
I may even have one I can sell. I talked to a friend about it today to make sure he doesn’t need it. If he’s all set I will contact you. It came off my boat, he’s been working off the payment in some labor and I thought it was for the radar but today he tells me the labor is for the plotter but may be interested in radar as well and will let me know in the next day or two