There are a handful of on-line stores, but all appear to be in the UK.

As far as tool size, the ruler along right-hand side appears to be in centimeters (the longest marks/lines denoting one cm). Projecting the scale to the entire length x width, appears your guess of 2.75-in x 1.5-in is close.

Here's US seller of what appears to be the identical tool. Width is incorrectly listed in description. Think it should be 2-3/4" x 1 1/2".