Rear sliding window seal?

[createthis]

Howdy folks,

I've been blocked on my rear sliding window replacement project for a few weeks now. I was wondering if you folks could help me get unstuck.

I accidentally broke the sliding window by using my softtopper as a makeshift hammer. No big deal, I thought, throw some money at it and it'll be fixed in a week. Ha. Not that simple, apparently.

I bought a replacement sliding window and seal from lmctruck.com, then I took it to my local glass shop. They were really hesitant to even talk to me about it. I guess they see this stuff a lot? I dunno. I dropped the truck off and they gave me a call a few hours later saying the seal was too big. I said, "email me a picture and I'll get a replacement from lmctruck." Here's the photo the glass shop sent me:



So, I called lmctruck, sent them the photo via email, and they sent me a replacement. When the replacement arrived, I took a picture and emailed it to the glass shop:



The glass shop said it's still too big. I called lmctruck again, and they told me: "Per our research department the seal should be larger than the glass. Once installed, the rubber will compress into the bodywork and around the glass and will seal correctly. The seal and glass install simultaneously, which can be extremely difficult."

So, my part vendor won't give me another part and my installer won't install what I have.

I asked the installer if they could cut it to size. They said they couldn't. It would leak if they did that.

How should I proceed? Thanks!