I've always checked TireRack to pick out tires for all my BMWs although I buy them locally.
https://www.tirerack.com
When BMW didn't yet offer Michelin Pilot Sport 4S summer tires, my service manager was able to get them for me.
If you're a BMWCCA member, the Roundel magazine often has $70+ tire rebate ads.
My M2 is garaged during the 3 winter months, but I once bought winter tires/wheels for a 3-series, but it was a waste of money due to little snow that year.