I totally feel you on the Iceland stress! I took my kit to some crazy rocky terrain and honestly the Gariz Design Leica Q3 Half Case Genuine Leather XS-CHQ3BK was a total life saver. It has this solid metal base plate that saved my camera from a nasty granite ledge... crazy loud sound but zero damage! It is super lightweight, handles the battery access perfectly, and ships way faster than most custom stuff. Love it!

Building on the earlier suggestion, you can totally find amazing protection without the Leica tax! Are you planning to use a tripod often for those long exposures tho? If so, the TPY Genuine Leather Half Case for Leica Q3 is a fantastic budget pick. It uses 3mm high-density cowhide that provides better impact dampening than some thin luxury cases. Love how solid it feels for the price!

Honestly, I get the paranoia. Iceland is brutal on gear. I would suggest looking closely at the LIM'S Design Leica Q3 Half Case Genuine Leather with Aluminum Bottom because it uses a 6061 aluminum base. That metal plate actually takes the hit instead of the camera brass. Most cases just have thin padding there, but the Lims adds substantial clearance. You might want to consider the seal around the battery door too... even if its covered, volcanic grit gets everywhere. Be careful with the Oberwerth Half Case for Leica Q3 if you have smaller hands, it definitely changes the ergonomics. For the Q3, make sure whatever you get has the proper cutout for the tilt screen hinges. I found the Arte di Mano Half Case for Leica Q3 is the gold standard for fit, but the lead time is a nightmare. Stick with the Lims for the trip, its the best balance of being built like a tank and arriving quickly. Just tighten the mounting screw with a coin so it wont wiggle.