Theres really no need for a 4 bolt booster as 2 bolts are really good these days! But if you wanted something lighter try the carbon 2 bolt trialtech booster. http://www.tartybikes.co.uk/product.php?product_id=10343
I would(As would many) recommend the Trialtech 2 Bolt booster. Its very cheap at just a smidgin over £20 and is also very strong and stopped flex completely on my bike! http://www.tartybikes.co.uk/product.php?pr...category_id=104