Note that the "downgraded" version isn't really much of a downgrade and will work exactly the same as the original. It has the same amount of memory to store GBA games. If I'm not mistaken, the only difference is that it has less SRAM memory. But it still has enough SRAM memory to store the save file -- it just can't store additional data in the SRAM about which game the save goes to. But that isn't a problem at all since the data is easily stored to the slot 1 microSD card. In other words, there will be no difference in functionality between the old and new versions.
The old version is obviously no longer manufactured, so there is little to no chance of getting one unless someone sells you theirs. It's unclear whether the new one is still manufactured as psxboy has been out of stock for months. sky2k.com was the only other place I know of to get them, and they are also out of stock.
Ironically, your best chance of getting one of the "old" ones (with the extra SRAM) is bundled with the DSTT, but those bundles are hard to find.
ebuyrealm.com still sells the eWin 2-in-1 and eWin rumble pak bundled with the DSTT for $45.99 (free shipping to the U.S.) which isn't a bad price if you're also looking for a DSTT but certainly isn't worth it for just the 2-in-1. I have no idea whether the 2-in-1 is the "old" or the "new" version (not that it matters).
The EZFlash 3-in-1 is really your best alternative at this point, and is available at dealextreme.com.
-Bri