Ask your Rega dealer about a cartridge. You're a good customer and he is well placed to help with sound advice and pricing.
I'm sorry to hear about the busted Denon. Cartridges are delicate, of course, and this kind of thing has happened to many of us. That doesn't make it much easier to take when it does happen, but welcome to the club anyway.
It would be great if your roommate both fessed up and paid up, but of course he doesn't have to do either. Just a thought, but if your new cart had a removable stylus, you could take it out when you weren't listening and keep it where your roommate couldn't break it.