I have a Cyclops DS flashcart from like 2007 that still works great. Some of the newer carts had time bombs on them so they could sell you another one.

I saw a DSPico on AliExpress earlier this year for less than $5 including shipping so I finally bought a new one because it works a little better on my 3DS and has slightly faster load times.

If you can still find the listing its a good buy.