Might be worth contacting the seller if it’s a rolling shell.
GENUINE 1998 BMW Z3M 3.2 Convertible. Genuine Z3M Bootlid Sold. Topaz Blue Hardtop with genuine fitting kit £1200. Centre console in black & blue £500. Bare Body shell. Breaking for parts. Tri colour M steering wheel £175.
www.ebay.co.uk
There’s a beam state side but would be near the same price as a brand new one, and what right trailing arms there are asking big money cheapest one state side.
Find many great new & used options and get the best deals for Damaged 1998-2002 BMW Z3 M Right Rear Trailing Control Arm Wheel Bearing at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk
This might be worth a trawl through or making a enquiry. There are a few coupe ones listed but if ///M or 2.8 I’m not sure
https://www.partrequest.com/catalog/control-arms-and-parts/bmw/bmw-z3?page=2
I hope you can source your parts reasonably but there is some greedy b*****s out there