No the Lg Arena doesn't come with a stylus but the LG Viewty and the Renoir both come with a stylus.
The stylus for the viewty and renoir does not slot into the phone like htc hd touch or most windows phones so you should be able to use the stylus off one of these 2 LG phones for the arena because there all touch phones.
it might not work with the call buttons but it should be fine with everything else on the screen.
you should be able to pick one up for around £5 including the stylus case.