x1 BMW E36 Hardtop - https://www.ebay.co.uk/itm/324055855979 - $200
x1 BMW E36 Hardtop Retrofit Kit - https://www.turnermotorsport.com/p-21241-genuine-bmw-retrofit-kit-hardtop-prepar-54218163061/ - $323

Kirk Racing Roll Cage E36 - $775
https://www.bimmerworld.com/Kirk-Racing-Roll-Cage-E36-92-99-3-Series.html