I have a smaller sized wall safe from Harbor freight that will hold a couple of handguns and jewelry, but I believe you're looking for a rifle safe. And I'm sure you've read the other thread running titled "In the market for a gun safe...", but since there've been no other responses I'll chime in
Look at this site:
They list one wall safe, V-Line 51653-SA Closet Vault, that looks like what you're looking for.
Another is a floor safe, BedBunker Concealed Floor/Wall Safe, and it's available in 36", 48" & 72" lengths.
Knowing the manufacturers, you may can find other vendors selling these.
Sorry I don't have first hand experience. I also am using a Stack-On cabinet bolted in and in a locked closet for long guns, but I don't have any high dollar firearms.