"What are some cheap ones that will work?"
The problem with finding a "cheap" drive for your B&W G3 is that it needs an older ATAPI (not SATA) model, which are very scarce now and - if new - are higher-priced than they were a couple of years ago. If you don't mind buying a used one, this Pioneer DVD±RW drive would definitely be bootable. I installed a Pioneer drive in one of my B&W G3s, because they were very Mac-compatible, compared to other third-party drives. The ebay-listed drive is less than half the price of the LG listed at OWC, so it may be worth buying. I bought a pair of (new) ATAPI Pioneer DVD±RW drives to keep, just in case one of my older Macs needs a replacement.