just cut it up yourself - a square/rectangular cake and a round one. Cut a slice off the round one to form a flat edge, stick the square one next to it and "draw" a number 2 in your mind. Use your biggest round cookie cutter for the inner circle of the 2 and try to keep the cake part at least 10cm across otherwise it gets a bit flimsy. You could also try drawing a big fat number 2 on a bit of wax or baking paper and cut it out to use as a template if you're not confident cutting by sight.
Number and shape tins can be a bit costly. You could even use an oblong / square roasting tin, just line it first. Make a template for the number or download a number 2 from the net and cut to shape.
Have you tried Lakeland? The other option is to get a big square mould/tin and then cut it to shape with a knife? The guy on Cake Boss makes it look really easy ;-)