I don't know how much weight there is in "2 pieces of lead" so I'm not sure if this will work.

Get some lead shot from fishing tackle or shotgun shell reloading supplier. Figure out how much shot it takes to match "2 pieces of lead". Take a little away from that pile and put back in bag. Drill/cut small (1/2 inch) hole in bottom side of wing tip near tip rib. Mix 15 minute (or longer) epoxy sufficient to mix with the lead shot you have out. Stir well, better to have a little extra epoxy than not enough here. Carefully trowel this mixture into the wingtip and stand the wing on it's end to get it all to the very tip.
Let dry and cover hole.
This can also be done in the first bay inboard of the tip and may be easier to patch since you have glass tips.

Is that an ARF or a kit?