I got 4 for £1.99 from ebay.
27 down to 9 Celsius. I use one on the action of my HW100 as it's so temp sensitive. The temp blocks are 3 degrees apart but you can use the changes of colour to nail it down to 1 deg. Also this works to extend the range a little (so even with a 9 degree lowest display, you can tell fairly accurately down to 6. I wish I could find a single small strip that goes from about 24 to -5 though.