Bit of a curve ball but if nothing turns up SH, perhaps have a look at the (rather lovely) Acepac frame bags Allen. They're a roll-top design and have a removable liner so are 100% waterproof.
Hello Allen, it looks like a large in your pic but it's hard to know without knowing the frame size.
This is a large.
It's 490mm along the top. 140mm high at the back. 200mm high at the deepest point and 340mm along the bottom before it heads up towards the downtube. Sorry for the poor picture.