Your best bet is to try the folks at Horizon Wireless. HorizonWirelessOnline.com - Horizon Wireless, The World’s Cellular Repair Center ß If they can't get it then you might try finding a mounting tape at a craft store that is simillar in thickness to the standard adhesive. I have never had mine apart so I am not sure how thick it is. Depending on how thick it is you can go to a hobby store that sells RC planes and car and ask for a product called "servo tape". You will likely want the real thin black tape, not the thicker foam tape.
I bought my new screen from horizonwirelessonline.com and it came with adhesive as well also came very fast, Does the 8320 have the square edged buttons like the 8310 or the slanted edge ones like the 8330? I have a screen for 8310 that I got from the website listed above I would sell for $10 plus shipping so like $11
Yeah, I know those lenses are cheap. I just think that since I already have a good lens, it doesn't make much sense to buy a new one just to get the adhesive. But, if that's the only way to get it, then i guess I'm going to end up with a perfectly good lens with no adhesive.
You could always check Home Depot, Lowes or Menards for some really thin double-sided tape. That's all the adhesive is... you just have to cut it into really thin strips... a small roll of the tape should last you a life time of lens replacements.