OK, just looked through everything I have... Unfortunately I dont have those particular covers on my PC. Sorry. You may want to contact him via originaltrilogy.com.
I did however find a set he recently did. He again used the Alvin artwork for the fronts of the OT, but redesigned the backs. They are different than his older covers (the ones you posted). He also attempted to create "Alvin-like" covers for the PT to match. They are interesting. They dont really look like artwork, but their neat covers. I'll get the set of 6 uploaded as soon as I get a chance.
I also found another set of Alvin covers by someone called "degeneration" I'll pass those along also.