I would try googling it e.g. searching for wallpaper strip + (your location)

Sometimes paint stores also carry some wallpaper strips. Hope you were able to find something.

A specialised wallpaper shop. I’m surprised Bunnings couldn’t recommend a supplier

Australia’s Wallpaper at 523 Whitehorse Rd,Mitcham.

Wow I’m surprised Bunnings don’t have them

I would assume Bath stores would hopefully sell them or eBay. good luck

I really like the ones at masters. They have good variety

I got ours at masters and they where so helpful as well

there is a small variety of wallpaper available at spotlight. Alternatively, you could use a stencil

Masters sells wallpapers – also gives samples so you can bring it home (a small piece ) to see if it is suitable

Google on line I have seen adverts with wallpaper as it is becoming popular again, but expensive.

Online and ebay stores tend to have all those other things you want but can’t find in the shops

Online search good way to get ideas and prices

Maybe trying a paint store like solver or stratco.
You could also check eBay or gumtree

Clints and such stores used to have them for $2 roll. Or perhaps put a Wanted to Buy on your local Facebook buy and sell pages. You would only need one roll to do a toilet, and people may have one left over from things they have papered. I know I have quite a few different ones in my craft room.

I was going to say Ebay but their are a couple who already said that

Masters have wall paper

I would try masters and eBay at least with eBay no leaving the comfort of your home

Masters. And Ebay

If you have Masters they have heaps of different wallpaper designs. they are basically the same as bunnings but they have heaps of other stuff too.