The majority of plumbing O-rings are to thick to fit you would have to slice them in half. Fasttech and Ebay are a good place to check.
I understand the situation its a tough one as O-rings are consumable items so its up to klarus discretion what they charge. Not a great way to gain future customers by overcharging.
The quote was for express shipping and not for the o-rings.
I have the best experience with the Klarus customer service.
Through GB I bought G35 and it was DOA.
GB absolutely refused to address the situation and suggested a slight compensation.
I wrote to CS Klarus asking for a driver, and Klarus sent me a free lantern for free.
According to my experience, this is a perfect customer service.