I'm in Canada and material is very expensive here too, about two times what it would cost in US.
Some online shop are willing to ship abroad. Even with a heavy shipping charge of 20-25$, sometimes it end up being quite a saving compared to buy locally.
I second the trift shop option. I have become used to go there once a week and the finds are always good. Old sheets are often excellent quality material and cost almost nothing. Look for the ones with a tag that tell you the country of provenance. Flannel made in Portugal is good and make nice batting. In addition, it's very eco friendly to recycle!