Welcome to the site !!
My first question is , what is wrong with the decompressor ?? , is the shaft bent or broken ?? , is the plunger bad or broke ?? ..... my personal opinion is I would swap the setup (tower ,everything , ) with a 02-06 450R or a 05-06 450X , which has the separate rocker to adjust the decompressor , and it will solve the problem , as the 08 R and X both have the same issue with the decompressor and continued to have it thru 09 , but the earlier models did not ..... , I have a 06 450X and have never had a decompressor issue , the bike is in the 3,500 mile range (single track trail riding) , and has never had any decompressor issues .... That would be my recommendation .....