I think if you want to learn as close as possible to the time allowed, your best bet is a 300 CBi. No training organisation in the world (not restricted to trying to find the cheapest helicopter to buy...ie the army or airforce) has ever used an R22 over a 300 CBi. Bristow (the largest training civil operator) uses them.
Not sure if there are any your way at though...
stay safe.....no negative 'g' with that rotor head please.....