While its not on the same level, check out the M6. You can remap the side scroll buttons, as well as the two other ones, which gives you four actions.

i'm using this mouse for over 2 years now: https://happort.org/mouse

it uses this board: https://github.com/jfedor2/rp2040-pmw3360 and i can dig into my .stl files for the mouse if you want... made it on Blender and https://ryanis.cool/cosmos/beta - it's not the most lightweight thing in the world (would say around 100 grams) but it slides nicely and maybe by cycling/exercising often i don't think this one would give me RSI at any point in time... it's angle based on the most muscle neutral position the human arm anatomy has, between 20° - 30° [0] https://www.jospt.org/doi/pdf/10.2519/jospt.2004.34.10.638

I miss my G602 so much. Replaced it with a G604 and then replaced that one with another G604 and then a third G604 before realizing that Logi's build quality has seemingly dived off a cliff for the premium they charge for their product and swapped to the 50% as expensive Keychron mice and keyboards and have been satisfactorily living with the decrease in available buttons (though quite an adjustment was needed). Onset of carpal tunnel has seen me switch to a vertical mouse anyways, so a change was inevitable.

My G602 died due to Logitech's infamous double-click issue. :(

I've been fine with the G502 X Lightspeed (which should avoid said double-click issue due to optical switches) and some more efficient button use to compensate for the fewer side buttons.

> a decent, modern replacement for...G602

What's wrong with the G502? I like the wired G502 pretty well. Ideally I'd tweak the shape to be a little more like the M500s shape, but I'm happy enough with it overall.