I'm afraid I don't know, I don't use them. Maybe have a search online for someone stocking them near you? I would've thought the supermarkets or boots would've had them in, how strange!
maybe it's just your branch of tesco? I have a biggish store and they stock the choc slim fast bars. Have you tried typing slimfast chocolate crunch meal bar in google then clicking the shopping option at the top?
I brought some from sainsburys on wednesday... i have just thrown mine away as they are soooo discusting they made me almost sick!(yucky yucky). Im sticking my shakes i think!