I've had same issue. Fiat can't source them.
They're M12, with 33mm eccentric washers, around 115mm long.
BMW part no 33326764292 fits & is available. The bolt is a bit longer (125mm) but plenty of thread so you can shorten if necessary. I'd recommend getting genuine BMW part as the cheaper Chinese ones I ordered 1st are rubbish quality & the removable washer doesn't key properly on the bolt.
Don't forget to soak all or your suspension tubes, inside and out, with a high quality anti corrosion liquid. They rust and parts are no longer available. Lanoguard is the latest fad. Waxoyl is pretty rubbish to be honest.
I used zinc plated high 10.9 spec tensile bolts with a half nut to lock in place and a thread cover cap to keep rust at bay for removal. I use the same spec for the bottom arm ball joint pinch bolt. Both are well coated end to end with a high spec anti seize.