Tungsten tubing, forget it, tungsten putty, no chance.
They don't manage these!
I got hold of as many Ace ones as I could when Ace got taken over by Shimano.
Slight modification to the rig, to work nicely for my purposes. Pop-ups to be honest can be a pain with Crays, who will rip anything bait wise apart, but I can use a mini soaked wooden ball, just not too long, or use, and dry it out again. The smell or taste of the bait soak then impregnates it.