The free and open source AutoHotKey (AHK) can do this very easily:
; do nothing, avoid spurious "up" events
#IfWinActive makes sure that the behaviour triggers only within that game. If the string "Tibia" is not in the actual window title of the game, you can use a spy application shipping with AutoHotKey to find a correct selector. This solution is purely event based, so has no performance overhead and does not lag behind if the PC is busy.
This can be arbitrarily extended. For example you can change it so that if you press another key, the behaviour is temporarily disabled, you could opt to act the 4th or 5th mouse button as a click-and-release left button, and so on. Have a gander through the AutoHotKey Usage and Syntax chapter to see what's possible.
AHK can provide plenty of "quality of life" features, only limited by your imagination. For example it can scan the screen for specific images/icons, and perform actions if it detects certain things, and so on. I'd highly recommend for someone who is limited in what they can do with mouse or keyboard to have a deep look into it.