You don't need to buy a physical copy, but.... I myself prefer to have one, because 1. it doesn't feel right to download games for free, which should be paid for, and 2. I love the series, so I like to own it physically. It was quite cheap, too, and I got it as brand new.
And yeah, just buy an R4 (one, which works with the 3DS [2DS is the same hardware]), a compatible micro SD card (I'm guessing all micro SDs are, not sure), download the rom, the patch, a patcher, and patch it, and copy it to the SD card patchpatch.
I actually just yesterday ordered one, I simply googled "buy r4 nintendo ds", and the very first link (r4ds-ds) took me to a site where I could buy a R4i Gold 3DS card. I've actually got 3 copies of it already, but my friend wanted one, so I sold him it, and bought myself another one. But yeah, it hasn't arrived yet, so I can't guarantee you the site is trustworthy. Oh, and I remember getting my other 3 copies for a much cheaper price, and they came with a USB adapter for the micro SD cards, but it was some German site, and I don't remember it's name anymore.
Also... if you have friends to play DS with, buy 2 and try out the fan translated Blood Of Bahamut ...it's concept is quite simple, but I LOVE it, I'm having a blast every time I play it, and it has become one of my favorite DS games ever. It's much better with 2 or 3 people though.
And if you're okay with jump scares, try both Nanashi No Games, they're full of charm, just like BoB.
Thanks for the fast reply! Thought this forum was dead aha.
I plan on getting a copy of the game anyway, trying to get a sealed version so I can keep it as a collectors item. Also if you don't mind me asking, where did you get your game from? Cheapest I can find it for is $10 used and $60 sealed.
And thanks for the recommendations, I'll check them out when I have the time