Couple of part interchanges I found.
During the time I've owned my SP1, I've come across a couple of interesting par interchanges with cars. I run a BMW (car) repair shop, and have access to Worldpac parts wholesale. They do European and Asian auto parts, all OEM stuff.
Anyway, my bike came with a Fram PH6607 oil filter on it. I recognised that as an automotive application and plugged it into my order program. Came back with a Denso part number that matches a 93 Mazda RX7 FD. Denso are made in Japan, very high quality filter. At wholesale, these babies cost me under $4 each.
Next up is the rad cap. Honda dealer wanted stupid money for it, so I did a little searching and came up with a cap from a 1992 Honda Accord. It's 1.1 bar, and uses the same seals and spring setup as the RC uses. $6 for a Japanese made cap.