Unfortunately, there aren't exactly a lot of products to do this for cheapo. You can build your own, called the Sanni Cart Reader: https://github.com/sanni/cartreader, that'd probably be the cheapest way to do it I would guess.
However, if you happen to have an N64 Gameshark, a parallel cable and a PC running Windows 98 that also happens to have a parallel port, you can actually dump ROMs using a Gameshark and a program called "Game Software Code Creator". You'll need Windows 98 mainly because the software doesn't work amazingly well on WinXP or greater.
Otherwise, might as well just download them elsewhere TBH.