Yes, the Series 2 Girling cap.GIRLING TYPE Brake fluid reservoir CAP - For all motorsport Rally | eBay
Compbrake Motorsport. ALSO AVAILABLE IN SMALL FOR INTEGRAL CYLINDERS. SEE CMB 0135-S. CMB 0135-L x 1.www.ebay.co.uk
I'd drill out the centre to fit the float. I've done this before