Ummm I forgot. Sometimes my brain isn't working.
This has 3 RTCs built in...
http://www.ic2005.com/shop/product.php?productid=119&cat=4&page=1and it has been out for a long time. I dunno why this eludes me so much. I own TWO of these things. I just haven't ever played GBA roms with it. I have it installed in my neoflash n64 cart and the other one is probably in my ..ohhh now I remember
I have two N64 flash carts from neoflash. Both have this product installed in them.
My genesis flash cart has a more inferior SD adapter card in it also. So I have 3 total and the various GBA carts for the other flash carts they make.
Hmm I should try it out and see if games work right. I guess this means I don't really need another GBA flash cart lol.
I just did some reading and this is mainly for the N64 flash cart but I think that means the one that came with the Genesis flash cart is more suitable for GBA and it costs a lot less money. Well I'll try the stuff out when I have time and see. I was getting ready to buy an EZ Flash IV, might even still buy one anyway. What I really want is KRIKzz new v2.1 PCE HU Card.

edit: just thought I would mention that NeoFlash sites are down for maintenance today so I can't really prove anything about their GBA flash carts for the time being. I managed to get the cart working with ROMs stored on 2gb microsd inserted in a SD adapter. Saves seem to get overwritten by each game though. Without the latest build of the menu, I'm not sure if this has been fixed.
edit again, I got the latest menu from their software revision 1.32 and I can comfirm that their device does indeed support RTC. However I have some small issue with the save file for pokemon emerald where you have to save twice so that the game saves. I have been reading that this is pretty much the only reported problem with their device. God their programmer is so touchy and finicky too. It took me about 2 hours to get this device up and running properly but it works now.