at least in the old days you could use on windows the ALT key to type the number of the letter (usually a 3 digit number). On Mac you can use also  ALT but it is slightly more simple: ALT+e and then e would give é, ALT+e and then a would give á

on linux you can type directly the hex unicode:

1) you have to hold down CTRL+SHIFT

2) then type X and U

3) now (still holding down CTRL+SHIFT) type the unicode hex (for example 00e0)

4) release CTRL+SHIFT (you should now see "à")

You don't need to buy a new keyboard. Under Mac OS and under Windows, and probably others as well, it's easy to set up different national keyboard layouts for the same keyboard. Unfortunately I only know the detailed procedure for Mac OS, but... OK, here it is for Windows 10:

http://www.windowscentral.com/how-change-your-keyboard-layout-windows-10

For the Mac:

System Preferences (gear icon), Language and Region, Keyboard Preferences. Under Keyboard, check the box "Show Keyboard, Emoji, and Symbol Viewers in Menu Bar." Under Input Sources, add the keyboards you want and "Show Input Source in Title Bar."

You'll see a little U.S. flag in the menu bar and under it you will see menus to let you switch to other keyboard layouts.

If you just need to add accent marks there may be another way to do it. On the Mac,  option-e, option-i, option-u, option-shift-~, and option-` act like traditional typewriter "dead keys." They seem to type a mark, but the next letter you type will be combined with it if that combined character exists. Thus: é, î, ü, è, ñ. 

So I have download an Italian Keyboard on my pc, or you can use one online.  http://gate2home.com/Italian-Keyboard.

One fast solution is to use the ' beside the letter, like "Luca e' biondo".

If you buy Italian keyboard stickers online, and install an additional keyboard in your OS, that could also work.