[Breakerfan]

I'm in the states, so this may not be applicable to you, but, I think I bought the last batch at Lowes's, which is a store similar to Home Depot. If you don't have Lowe's up there, keep checking any big box hardware stores, or maybe even a plumbing specialty shop in your area. If you want to order on the internet, smalljoes I believe has them, or even amazon... just do a google search for #7 o-rings. There should be a local supplier to you that will carry them.

I use #9 and #10 though, I think #7 would be too small.