DX does sell all flashcarts including DSi version. They just don't list them anymore so that when someone tries to search the site they end up with nothing. Just google the cart name and dealextreme and voila. You have your product
DX just has interesting delivery times which is the main reason that it is pretty hard to get refunds and such quite quickly.
BTW CycloDS has been for sale there for a while now and seems that the prices do change a bit from time to time. Then again I found a local internet store here in Finland which sold CycloDS Evolutions for ~30 euros. Now that's quite cheap compared to the normal ~50-60 euros.
//Qtis