Penzance is really not hard to come by, as I just got 7 of the 8oz bags last week with just a few phone calls, but no one seems to want to put out the effort of making a few calls around to the online retailers. I've got another 4 coming as well. All you have to do is make some calls. :wink:
You can try "Quiet Nights" by G.L. Pease, which is in the same flavor family, and would be a definite substitute. There was a thread on here last year which is a mirror image of this one. Al has already mentioned Larry's Blend. Some people like Plum Pudding as well, as it has a similar flavor. Ten to Midnight to me is just a little too strong to have that smoothness of Penzance, but not bad at all.
But....Penzance is unique, and that's what I love about it.