Need to find a Memory Card for Mio C310X Digi Walker

Hello,

I have two very old Mio Digi Walker GPS devices which I was able to unlock and use voice directions. I had everything put onto 4 GB TOPRAM SD 150X memory cards. I now only have one 4 GB TOPRAM cards left that are functional. I have other TOPRAMS that no longer work. I copied the working TOPRAM card onto a new Verbatim 4GB SDHC card. It did not work with either of my Mio GPS devices. The good TOPRAM card works on both Mio Devices. Does anyone know where I could get an older memory card that would work or have an alternate solution?

Thanks.

RnT