I'd call a couple of them. George Merrill at Artech, Eric Holmer at Race Place might be. two good ones to start with.
I'd also call LEKI USA. Number is on their site.
I think the issue is that LEKI does not want customers replacing their own tips. I think they want that kind of repair only done buy a professional in a LEKI dealer's back room. Or, perhaps ij their own customer service room. That's just a hunch.
You may be able to get them, but it's not going to be through on line ordering. Or, you may get suggestions on who can replace for you.
Sounds foolish, but it may be what it is. I've replaced tips on these, Swix and Komperdell poles...all used by my family. And in with LEKI, I bought the tips from a friend who is a dealer.
Good luck. Think you'll find a couple of calls helpful.