Caterpillar 287c sliding window issue.

Hey all, Chasing some advice, I've got a 2008 287c skidsteer which one of the sliding windows keeps falling out when it's opened. I've put this down to the seal/rubber being just about stuffed. Had a quick look on the cat sis spare parts and they are asking nearly $400 for a window seal kit. Does this sound legit? Or is there another way round this issue apart from keeping the window closed. Any advice would be greatly appreciated. Thanks.