Can anyone recommend a cartridge for me to pick up for it? I really don't have the hundreds of dollars that everywhere seems to be asking for a B&O cartridge, so I'm trying to balance quality and price.

I am afraid that they are "hundreds of dollars".

B&O no longer manufacture cartridges full stop.

You need one of the MMC20 series. I cannot recommend s/hand from eBay as most will be a rip off. Your only sensible source of new is www.sound-smith.com where you will get a warranty and an excellent product.