where does one buy leadshots for loading spkrs?

as you can see, i am somewhat new to this hobby. i have a pair of totem arro's and trying to tighten the bass by loading down the speakers. there is a hole in the back and i assume that is what it is for. i was told leadshots work better than sand or better yet a mixture of both. any inputs pertaining to the arro's will be welcome.
curtis. p.s. i use a rega planar3 with audiotechnica m44e and heavyweight on the rb300. also a bryston b60 and an acurus phonostage. much thanks.