This rifle doesn't have a weaver rail. It's a 3/8 dovetail.
I'm using Hawke Match mount rings, medium height.
My scope is 44mm and it's a perfect fit. It would be still OK in low rings, but the cheek weld dictates medium for me.
Check some stores specializing in air rifles, it's a popular size for the rail, and they usually have a selection of good quality rings that would fit.
I know that dlairgun.com carries the rings I have and they are in Vancouver. These rings are available both in 1" and 30mm and also both for dovetail and weaver, so make sure to order the correct set.
Amazon carries UTG (Leapers) rings, that are cheaper, and still relatively decent.