Quad tips are 4.4i only.
Nothing that would look good if you don't cut and re-weld.
These are the only non-welding tips that will work =>
BMW Exhaust Tips x5 Stainless Steel | eBay
If you look closely, there's a cut-out on the bottom of the tips for your OE tips to protrude through. I've seen this in person, and it does NOT look good at all.
I've tried the "cut & re-weld" method and was OK with it for a while, but ultimately replaced it with a Remus exhaust.