I use Redline MTL in my trans. I haven't had any problems shifting cold, or warm.

I just ordered the oil online. There are any number of sources for Redline, you should be able to find it for about $8.00 a quart.

If you are having trouble shifting when it's cold, be sure to check your clutch fluid. It's just brake fluid, and that's hygroscopic. Over time your brake fluid and the fluid in the clutch line will absorb water. The water migrates to the bottom of the system when you're parked. In the case of the clutch, this is the slave cylinder at the clutch.The result is a mushy pedal since the wate will compress but the brake fluid won't. Cold makes the problem more evident.

Bleading the clutch system might solve the problem.