There's no infinite items glitch, but you can duplicate them.
Look in the Glitch Guide and/or the Missingno. FAQ and research what you need to do in order to find Missingno. From that point on, it works the same as a Red/Blue Missingno. and will allow you to duplicate items. --- Why bother making a signature?
I've tried that I've used the Mew glitch and ran into a bunch of Missingnos but every time my game freezes so I turn it off and try again but at a different special rating but every time it won't work. If you or anyone else knows exactly what special level gets me a missingno that won't freeze or mess up my game let me know.
Just found out something every special works that gets you a Missingno. If it don't work the first time just keep doing it and it will eventually get you a normal Missingno and give you over 100 of whatever you want.
So if it freezes or starts acting goofy just restart and do it again.
The 2 trainers I know that give you a Missingno. are swimmer 2 underneath the Fuchsia gym and the guy in the very east corner in vermillionwith the other trainers in the grass. He has a Growlithe and a Vulpix.