Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5463422.
I picked up a Cabela's telescoping rod at a garage sale, and it was missing the endcap. This design threads in where that went. I don't know how well it matches the original, because I've never seen it. Rod details:
Cabela's Graphite Composite Telescopic Rod Y-16237060-001-6S
I printed it out of PLA. I expect PETG would be better, but I don't have quite the same precision with that. Once I get it tuned, maybe I'll try. PLA+ may be a good option as well.
Print with the open-end flat on the bed and the cap up. No supports. 100% cooling to support the thread overhangs (this is where PETG may have trouble).
As you can see, I used matching black, but it might be fun to throw a color down there. Traffic-code orange or similar.