If you want something like a F1 gear shifting system.....you'll need to buy a complete new gearbox....if I'm not mistaken Hewland has one....but also try X-trac. These are racecar gearboxs and are very expensive. For road cars the most comon if sequencial gearboxs....you could try adapting one...from a FIAT, Alfa Romeo, BMW, etc....but changes are that it wouldn't fit in your car.
It's hard to change a gearbox in a normal roadcar cause the car is built around the engine/gearbox that it has originally...so probably the only thing you can do without having to change gearbox is change it to sequencial....luckly you might be able to change it to semi-auto (like F1) if your car has the space under the hood for the semi-auto actuator. But probably you'd have to change some gearbox internals (selector drum).
Well I'm not a specialist....this is my opinion.