there was a thread on this some time ago, and I bleeb that it will fit.
I'm in the process of having a solid gold one made for my LEAL and possibly a silver one for my BCB AL.
(see my thread on the general discussion forum headed "a question for you mechanical type person")
The thread size within the knob is 10-32 UNF (also quoted as 10-32 NF).
I have a very cheap "Strat" type guitar and the trem arm is knurled rather than threaded so I dont think I'm able to positively state the "make up" of a Strat knob,but it is identical to the EB and is threaded 10-32 UNF too.
I'll have a dig about and come back on the metal knob if I find anything.
There is this link
[ame=http://www.amazon.com/gp/offer-listing/B000J33ZO6/ref=dp_bb_a/002-2644653-7186448?ie=UTF8&tag2=dealtime-mi-mp-20&redirect=true&condition=new%2F]Amazon.com: Used and New: Tremolo Arm With Chrome Tip, Hardened Stainless Steel, fits USA Tremolo[/ame]
which I got from this previous thread http://www.ernieball.com/forums/music-man-guitars/19288-next-pimp-my-ernie-ball-music-man.html
Here's a good one
[ame=http://www.amazon.com/s/ref=nb_ss_/002-0313834-8228063?initialSearch=1&url=me%3DA1YL6JT47QH4O4&field-keywords=tremolo+knob&Go.x=0&Go.y=0&Go=Go]WD Music Products @ Amazon.com: tremolo knob[/ame]