Gravity cistern, no pump, need select higher pressure

[archaic]

Is there a way to increase the pressure only to our toilet tank? Something that would simply be inline of the toilet tank supply line (between the shutoff valve next to the toilet and the toilet tank)? The cost of water, and the lack of problems with the dish and clothes washers means we aren't interested in increasing pressure to any other faucet/device except the toilet. Well, actually, to an bolt-on bidet we are looking to buy.