Up/Down/Side-grade to X2?

How does one go about up/down/side-grading to X2 (I have both X1 and X3)? It's not an option at the store since X3 came along.
 
I'd really like to get my hands on R-Mix. How I missed that when X2 was current, I don't know. I wouldn't have skipped X2 if I'd realized.
 
I emailed Customer Service about a week ago, but I'm assuming they're backed up.
Any suggestions? Ideas?