I got my Beeman Sport Aperture sights, and Match front sight from here;
http://www.dlairgun.com/ The Match front sight for the 48-54 isn't listed on the sight, but they have them.
The factory front sight will work, but I find it WAY to wide for precision. Just make sure you follow the instalation instructions when mounting the Beeman/Williams sight. Good luck and have fun.
Mulby