Buy a cheap external DVDRW and get done with it. You might need it again later in case you ever have to format, you'll save yourself the big ISO downloads.
This is why I ordered mine today, it was only 40USD 🙂
Edit: Just noticed your sig. Doesn't Lion come with a new feature called 'Remote Disc'? Did you try that? I believe it lets you access your other PC's disk drive through wifi.