The ones in the edc site say they are 6mm X 1mm but it doesn’t say if the 6mm is the inside or the outside diameter. FastTech has some that are 6mm ID X 8mm OD X 1mm, if that is the right size (SKU 1536601). Can you measure the diameter you need? This thread seems to indicate another size. DQG III o-ring
There are other o-ring manufacturers that you can find on Google but I don’t know how easy or affordable it would be to buy just a couple from them.