make a new one, the most commercial rear clevises are made from heavy cast iron. make a new one from hdpe or nylon. you also have 3 90 degree bends (one on the t). if you put a female 1/2 bsp push fit to 12mm pipe then bend it round into your valve it will provide alot more flowrate.you can put a t in the 12mm pipe just make sure the tube from the buffer tank to the valve goes accross the straight part of the push fit.

the flowrate of 8mm tube is only 7.75 l/s, is it possible to go up to 12mm? the tube size is probably the limiting factor in your system. also how big is your ram?