I was wondering if any manufacturer makes bricks whose top is not flat but slightly slant to be used for window sill for water drainage. I have seen slant window sills made with regular bricks that seem set in mortar at an offset but I'd prefer if they came with a slant. Is there a name for slant bricks like that?
There may be a brick that has that shape already, but I have not seen any. If there were, they would be custom ordered. To match your brick you have in place would even be a taller order. Bricks made in one time of year under the same name will differ in color and texture to a degree from brick of the same name from the same company, just made at a different time.
If color difference it not that big of a deal, you may want to go in a different direction.
Cast stone sills come in a variety of colors, but typically mimic the color of Vermont or Indiana limestone. They can be tailor made to suit the space it occupies.
It looks like Glen Gery has a line of cast stone, perhaps ready to go. You may be able to order stock long lengths and cut to fit. They are usually made to order that I am aware of.
You might be looking for "plinth stretchers". Some of our sills are made from these (UK). See for example special shaped bricks.