Where do I purchase online, Maldives, Mauritius, and Seychelles currencies to sell to them before they arrive at those destinations? Do those islands embassies in Malaysia sell the currencies?
Note that the following is based on random web searches and not based in any first hand experience:
From an answer on this 6 year old thread on Trip Advisor:
... you can't buy rufiyaas outside Maldives, and you can't sell them...
You don't need rufiyaas at a local island either, it's enough with usd,..
This Holidify website says something similar:
Outside the Maldives, Rufiyaa can neither be purchased in advance nor can be exchanged for any other currency after you've left the Maldives. Also, Rufiyaa obtained from ATMs won't be changed back at the currency exchange counter so you wouldn't want to end up with a lot of remaining Rufiyaas.
But it does mention:
The Bank of Maldives Foreign Exchange counter, which is located in the Arrival Hall is the most convenient and dedicated foreign exchange counter. Only major currencies are exchanged for the local MVR
You shall find some ATMs in Male, which will help you replenish your travel cash in case you run out of it. Please be advised that the ATMs only dispense Maldivian Rufiyaa, and that money obtained through ATMs will not be exchanged or repurchased in the currency exchange booth when you leave the Maldives.
However it also mentions using USD
To simplify, you will need MVR only for the local shops and services in the inhabited islands. Since credit cards and/or USD are widely accepted in almost all the places including some inhabited islands like Male and Maafushi, there's no need to carry too much local currency. Also, note that a credit card payment fee, up to an additional 5% depending upon the payment processing company, may be applied to the total value of your bill.
So it seems that you can only get the Rufiyaa's in the Maldives, but that you only should get it if you have a compelling reason.
Again this random website suggests getting the Mauritian Rupee in Mauritius. But I'd bet you could also get by with USD
A totally different website says this about the Seychelles:
Oddly enough, the rupees you will get from ATMs are somewhat useless. You can use them in certain shops and restaurants or for transport by bus or taxi, but not for much else. It is the law in the Seychelles that tourists pay for hotels -- including meals and drinks had there -- with cash in the form of major foreign currency or credit card.
Many activities and attractions, car rental companies and car services also fall under this rule. The Euro is the most widely-accepted foreign currency, and you will see prices listed in both Euros and US dollars. Also, you can bargain down prices if you use euros in certain places, like small hotels. The United States Dollar is also acceptable, but not as favoured as the Euro.
So you are expected to not pay in local currencies. And they also note this:
If exchanging currencies, do it at a bank, authorised money dealers, or with your hotel cashier. It is a criminal offence to change money with any person or business other than those authorised to do so and who are mentioned above.