WTB: Powerbook 520/540c powerpc upgrade

Looking for a Powerbook 520c/540c powerpc upgrade. Speed and manufact. of upgrade does not matter to me. I want to upgrade my little 540c again, so i am able to get some more use out of. I am willing pay out cash or trade something in my collection. Please pm me, post here, or shoot me an e-mail at: slaymaker@excite.com