Anyway, Rainbow and Delphin seems to be 2 completing brands in Singapore. Both cannot be found in stores but are sold via product demonstration which the sales person goes to your home.
They both sell on the idea that regular vacuum cleaners cannot suck the dust out of your mattress. Usually, the sales person will use the vacuum on your mattress and show you how much dust their vacuum cleaners can suck out. It is also mentioned that Rainbow or Delphin vacuum cleaner can double up as a air purifier as well.
Anyway below are the websites to Rainbow and Delphin if you are interested to find out more.
http://www.delphin.sg/
http://www.rainbowsystem.com.sg/
Personally, I feel that spending $2000-$3000 on a vacuum cleaner is way too expensive. With that amount of money, I could get a regular vacuum cleaner for the floor, a full fledged air purifier and a dedicated dustmites vacuum cleaner for the mattress and sofa.
Just got to the stores, should be able to get a good floor vacuum cleaner and a air purifier for about $200-$500 each. Do remember to get those with HEPA filters.
A good choice for dustmite vacuum cleaner is this RAYCOP UVC ANTI ALLERGY CLEANER AP-200 HERA which also have UV to kill bacteria and other microorganisms. It is available in the stores also. (Audio House, Best Denki, Courts, Gain City, Harvey Norman, Parisilk, Robinson)
Here's the website to find out more.
http://www.raycop.com.sg/
Cost? $200-$300.
Btw, for more choices, there is another brand for dustmite vaccum cleaner - Atocare UV Vacuum
http://atocaresingapore.com/