For years I've been using the Gigabeat U to make line-in recordings of a few events that happen on a weekly basis. I rely on it so much that at one point I bought a second unit in case mine ever gave out or was low on battery power when needed.
About a month ago, one of my Gigabeat U's became inoperable - on power-up it just the display reads "database error". Good thing I have a backup... until yesterday, the backup did the same thing. In the first case, I had tried the only obvious option available - the reset button, but it didn't help. It changed simply to show "gigabeat" and logo for a longer period of time and go black without ever showing "database error".
I've gotten a lot of good use out of these recorders, I'm happy to purchase a new one, but why I'm digging into this is that I have a valuable recording on the recorder I most recently used that I'm trying to acquire if at all possible.
There's no follow on model available from Toshiba so eBay may be your best bet for a like replacement.
That said, your long term needs may be best served by taking a look at similar types of products (media player with built-in mic for audio recording) that are currently in production by other vendors. Sorry that Toshiba doesn't have a solution for you today in this product category.