Speedo problems

[76bonanza]

I have had speedo problems since day one. Threw out cruize control box and got a single cable helped alot lubed the cable help alot but now I have a new problem.

I have a very fast bounce almost a vibration about 3 mile hour bounce thru the intire speed range. Also it will not return to zero when I stop unless I pound on the dash.

What are my options can I rebuild it? Get a new one? Any where to get good used ones? I have seen them on ebay but my end up with one worse then the one I have.

Thanks