You can use the same type of water bottle and pump used in your windshield / head lamp washer system. For testing purpose , you can simply re-run hoses to your existing washer system but don't forget to disconnect your wipers.
For spray nozzle, you can get it as agriculture and fumigation supplies store. It must be constructed of aluminum or brass to withstand high temps under hood.
DO NOT install high density fin condenser and water spray in combination. Water will get lodged in gaps between fins and block air flow. Your existing automotive condenser is more than enough for water-spray type heat exchanging. Automotive condensers have much wider gaps to permit airflow at low speeds and reduce frequency of clogging with dust and insect. This severely compromises efficiency.
This is called tube and fin type condenser. Effectiveness is determined by thickness of individual fin and fin count per cm. A unit with really thin fins can pack a lot more of them in per cm without compromising airflow. Same type of condensing coils are also used in your home AC window or split. A few companies in Pak manufacture high quality condensors like these for domestic and export market. They are available in almost every size you can imagine. There is also an American company making coils in Pak. Forgot their name but long time ago i saw their advertisement in a magzine
Those who preach relations of engine displacement with AC performance are following the route of typical "Jahill" mechanics of Pakistan.
In caravan air conditioning, small 5.5-8 HP, 3600RPM engines are used to spin automotive compressor usually Sanden SDH7 or Denso 17C and small 12V alternator to power system electronics. These units are rated for 20-24K btu which is a good 2 tons and can set you on ice in summer. Compressor is directly coupled to shaft where as alternator is belt driven are reduced speed of 2400 RPM.
Final show down, it takes 5HP to properly air condition mehran if you fix all other loopholes.
Well i forgot the most important part. Effective heat loss at condenser will subside compressor loads resulting in increased compressor life, reduced acceleration loss usually associated with air cond. in small cars and frequent compressor cycling leading to improved fuel mileage.
If you are really brave, you can charge propane in your AC instead of R12. Cooling curve of propane is similar to R22 while working with pressures of R12 system. Beware that propane is highly flammable. Any external leak would simply vent gas into atmosphere but any internal leak could transform your car into bomb. Particularly if you smoke. Lit that ciggy and bammm!!! you're gone!!! Safety tip for propane conversion is to replace all flare type fittings inside passenger cabin with permanent welding and carefully leak test refrigerant circuit under high pressure. Added benefit - propane is less capable to leak and is lot cheaper than R12. A properly secured system would be as safe as any R12 or R22 system.
Last word of warning. R134a sucks. It requires higher working pressures and steals more power from engine. Very bad for small cars. Its pain in ass to work with and usually best systems are only factor fitted with perfect equipment. Your average shed ac mechanic of Pakistan can never afford those equipments.