Commuting between La Jolla and UCSD

I think the best way to commute between La Jolla (more specifically La Jolla Village Lodge) and UCSD is bus 30. According to the MTS website there are 3-day passes (this option would be perfect for me. )). I think I need a compass card to load a 3-day pass on it. The above website stated that there are no locations where I can buy a compass card near the hotel I mentioned. What options do I have? For example, Can I buy the card on arrival at the airport? (I'd like to avoid using the MTS app as much as it has terrible ratings and also because I need receipts that I'm not sure the app offers.)