The Primus/Coleman screw tops seem far more available than Camping Gaz easy clic CV cartridges - I ended up going to Amazon for the small cartridge as none of the stores I went to had the smaller CV. Down side of the CV system is the burner is 500g, compared to my travelling companion's Ali-express burner that was 50g and worked well on the screw top cartridges. Might look into a different system going forward, mainly due to weight - size was OK, weight not.
As for locking bikes, the three sites we stayed on we just used cable locks around the bike/fence. The sites were quite remote though. I did bring a heavier Bordo lock, but that didn't get used (again heavy).
Whilst we were camping for a week earlier in August (not bike packing in my case), I noticed most bike packers weren't locking their bikes, even on a busy-ish site.
Note to self, ditch anything that adds to weight, so big lock, shaver to go. The weight wasn't an issue on road, but our route was over 50% rough tracks and trails, and the weight was an issue.