You're bound to find something that suits you in the Zowie range. They make eight mice, all with identical features, all with perfect sensors and all based on subtle variations of the Intellimouse shapes.
The EC series is based on the IME 3.0, which has an asymmetrical shape. The FK and ZA series have a symmetrical design based on the IMO 1.0, with the ZA being slightly taller to suit palm grippers.
I replaced an 2001 or 2002 Intellimouse with a Sensei a few years ago. Then it broke and I got a warranty replacement (upgraded to the full model). Then THAT broke and I replaced it with a Logitech (which is fine, although I spilled coffee all over it).
Meanwhile, the Intellimouse is still 100% functional in my laptop bag.
I lost one Sensei to a persistent squeak of the wheel, but the one I have now has been working for me for a while now. I still have an Intellimouse in fading white-to-yellow but it's like having a classic car -- I'm not willing to take it out for a drive.
My Intellimice last for a few years but eventually either the rubber coating on the scroll wheel detaches or the left button starts occasionally double clicking instead of single clicking.
IIRC mine once had some issue with the scroll wheel that I fixed by removing a dust ball and / or applying silicone grease. Silicone grease is great for lubricating anything plastic.
Sadly SteelSeries cant figure out the scroll, uses very cheap design to minimize part count (even on top $100 model WTF), and in effect scrolling down develops a squeal when clear plastic shaft supported only on ONE SIDE does micro skips while rubbing on bare $0.1 microswitch surface
Even when sold "new" now (https://www.newegg.com/Product/Product.aspx?Item=N82E1682610...) they seem to be old stock or factory seconds and do not sit level or have one or more broken buttons.
Any suggestions for a replacement? The new Intellimouse Classic does not have the right side button.