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Used a small crochet hook to remove the knot at the end of a tent pole so I can replace the elastic cord in the tent poles. My backpacking tents use 1/8 " cord and is sold as bungee cord.

I brought my Half Dome poles to REI and one of the reps showed me how to replace the cord (while selecting a slightly larger gauge of cord that ended up being less than optimal). Even after watching a YT video, marking all poles to insure proper reassembly, etc., I still goofed it all up. Learned an important lesson about proper storage of outdoor gear, though.

look into a tent that uses your trekking poles...

@tibber
According to Dave Baker of the Summit Hut, the shock cord will last longer if you begin your folding of the poles in the middle of the pole rather than on one end. This will not help your current problem, but could prolong the cord function in future for you.

@tibber
REI has no plastic clips to sell you if any break. REI refers you to "go online".
I owned the Quarter Dome SL! briefly. I didn't like the really thin material used for the tent floor. The footprint was also a lame product. I sold my tent on eBay after 3-4 nights in the tent & replaced it in May 2020 with Hilleberg Enan (Dark Green) only 3 days B4 they ran out of inventory. Backorders now take 1 year to fill.

tibber wrote: No, it didn't break, it just stretched.

I've restrung a couple sets of tent poles with new shock cord. It was fairly easy, apart from pulling the tips out of the end sections, which required some grunting and a furrowed brow.

Thanks to @chumley we were able to re-cord the stretched area. It had its challenges but was successful. And yes, there may have been a "furrowed brow" involved but nothing a beer couldn't soothe over.