Had to order them from the US Amazon :( Only the Calma ones seem to be available in Dubai.
I ordered mine from UK Amazon - are you after the wide base ones or the narrow ones (US ones are wide UK ones are narrow).
If you're after UK ones I have four boxes of slow flow which are brand new unopened (8 nipples) I am about to sell them - was going to put them on Breastfeeding Fun and Marketplace on FaceBook - my baby won't take the slow flow anymore so I had to order medium flow and silly me stocked up with the slow ones!!!
UK
http://www.amazon.co.uk/Medela-Medium-Silicone-Teats-2-Pack/dp/B003CKBAGI/ref=sr_1_1?ie=UTF8&qid=1431615163&sr=8-1&keywords=medela+teats
US
http://www.amazon.com/Medela-Wide-Base-Slow-Nipple/dp/B002SDD7LQ/ref=sr_1_2?ie=UTF8&qid=1431615205&sr=8-2&keywords=medela+teats
The bottle caps (little lid bit) are not interchangeable so you need to get the right ones for your bottles or buy an entire new cap.