Only option that I know of for supercharger is a Rotex unit. Yet they expensive and apparently not that reliable
Not entirely true. The rotrex is the only easy fit option, and in many cases can be cheaper than a turbo. The only reason they can become expensive is if the Rotrex fails. You can't rebuild a rotrex, whereas you can a turbo unit. Reliability is fine if looked after like most things. @
WillyWonka has done over 40k in his.
OP - I am about to supercharge mine. In terms of looking for what to buy we need an idea of budget / what you want the car for. Are you looking for high numbers? Or usable power on track. Either way, I'd budget in a Limited Slip Diff aswell, and some braking upgrades. So if you are buying a car, check for these. Also, the mapping. A well mapped car can make the difference between nice, usable power and lag etc. It is also the difference between the engine going pop or not.
Need some more info, but in truth, turbocharging or supercharging a clio is probably the last modification I would do. Plenty of other things to do to it to make it 'fast' before boost.