For shaving on top of pasta, you want white Alba truffles (tuber magnatum Pico).
You want 6-7 grams per person. When fresh ones are available, you can often find small ones. Be sure they’re highly aromatic, though, otherwise you’re just throwing money away.
Once you start shaving the truffle, it loses its aroma quickly, so buying one that’s partly shaved is throwing money away.
The truffle vendor I talked with last week said they’d received only very small amounts and expect them to start coming in in quantity maybe next week.