I brought my chain from Bullivants
. They have a wide selection.
The chain has worked perfectly, but then I brought it before I knew there was "good" and "bad" chain. This is Australia. If Bullivants sell it it likely will be just fine.
125 metres of 10mm gal chain is going to be quite a weight, and their warehouse is right out in the sticks. You'd need a car (or a friendly courier), trolley and some way of getting the chain to the anchor
Best would be to take a few links of your existing chain out to them.
From memory they're friendly folk, but not wise in the ways of cruising yachts.