The Ortofon OM-5 looks like a good bet money and sound wise. I am however confused by the sales blurb;
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Ortofon OM 5 Cartridge From ORTOFON in Denmark. This phono cartridge features standard 13mm (1/2"

mounting centres to fit all tone arms and head shells. The cartridge is
fitted with a quality spherical diamond stylus to provide a long service life and has a low tracking weight.....
Specifications:
- 20Hz to kHz + 3dB
- Channel separation 22dB
-
Elliptical stylus...
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A Spherical stylus... no wait! its ellepical!
However, if they say its not suitable for scratching, I'd assume that it is elliptical, which is fine for mixing.
Just bear in mind that with any cart/needle... you have to set them up properly.. provided this is done, all should be mint. Your SL-1210 came with a headshell, right? you'll need one for that type of cartridge.