That's a common style of Bullnose brick. It shouldn't be too hard to find.
Try local places that sell products like brick, block, pavers and other masonry supplies.
Instead of chiseling the mortar off, you might do better cutting it off using a diamond masonry blade. You can get ones that fit on a circular saw. They come in segmented or continuous. The continuous are better when cutting right next to the sides of the brick, as they are less likely to chip the brick.
Example1.
http://www.homedepot.com/p/KING-DIAMOND-7-in-Diamond-Tile-Blade-2-Pack-C70-2/202585392
Example 2
http://www.homedepot.com/p/World-Di...-Wet-Blade-for-Circular-Saws-DCR7-D/203615221
Note that some blades say wet cut only. These blades are thinner and can warp if overheated. They can be used dry, but you have to be careful not too cut too long without taking a break to allow the blade to cool down.
Example 3
This is a "Turbo" style blade, it says continuous, but it is not as smooth as a tile type blade and might be more likely to chip the brick when cutting right next to the sides.
http://www.homedepot.com/p/World-Di...Turbo-Blade-for-Circular-Saws-TP7-D/203615218