For the least problematic and most compatible brand DVD±RW drive for use in Macs, I'd recommend a Pioneer drive, like this
one. You can use other brands (like NEC, Samsung, or LG), but bootability can be iffy from one brand to another. Some of the major names (like Sony) sell rebranded drives, so you never know what product you'll get from one model to another, even with the same "name" on it. You don't need to restrict your search to Mac dealers, because your G4 uses the same DVD±RW drive as PCs. A Mac dealer may include (third-party) Mac burning software, which the drives marketed for PCs won't include. As for a floppy drive, you'll have to settle for an external USB version. Unlike their PC counterparts, older Apple FDDs had a single ribbon cable that conveyed data and power. There isn't any means to connect one of these to the standard interfaces found in the B&W G3s and newer Macs. With the cost of USB flash drives now less than $10/GB, why do you want to install a FDD in your G4? Is it intended for temporary use, until you've copied the contents of older disks to another medium?