Hi Yu Hock - welcome to the site. When you have a moment, can you please change you user name to you real name. We request that of all members here.
There aren't too many blanks available with what you're looking for. It's the butt joint that makes it difficult otherwise you have heaps of options. On that may fit the bill is a SEED PE5 popping blank. If I remember correctly, they have a blank about 7.5 feet long that is around PE5 and has a reasonably progressive action