There is a specific lens Hood for almost every lens. On most lenses you get the Hood with the lens, on others the manufacturer doesn't give you one, but will sell you one if you want.

:nono: :razz:
If I needed a replacement hood, or even just a Hood for a lens that didn't come with one, I would find the model number of the original, by putting say 'Canon 50mm 1.8 II lens hood' into a search box. With the answer I would then see what the best price I could get for the Canon one, in this example, and the do a search on eBay for the model of Hood, and see how much the copies are. If the price difference is large enough, I'll get the copy. :shrug: It's not that hard to copy a Hood, seeing as the can copy something as complex as a iPad.
For the price they cost to make, reflected in the price of the copies, with, you would imagine, a large mark up for profit, it is a bit naughty and cheap not to get one in with the camera imho.
No doubt someone will be on that you shouldn't buy copies, and that the Hood wouldn't be as good as the manufacturers, but if they weren't trying to rip you off by not including one, then you wouldn't have to consider an alternative. :shrug:
Just done a quick search for a Canon ES-62, (for the Canon 50mm 1.8 II) and it came up for £17.11 on Amazon. Did the same on eBay, and one came up for £1.41.

I know which one I'd buy.
You pays your money, you makes your choice.
I would say definitely get, and use, a lens Hood for all of your lenses. Most can be reversed and put back on the lens, and so not take up much more room in a bag, but offer so much more in return. :shrug: