"Brand new", yes it is hard to find them "brand new", because they are no longer made - you have to find a supplier who has not yet sold through their entire inventory, which is unlikely that they wouldn't have blown them out before now. RAID cards rarely fail, so I think it is probably a waste of money to buy a card "just in case". IF it does happen to fail, you can be a refurbished one easy enough. If it is downtime you are worried about, I would be MUCH more worried about your older server hardware (especially power supply and actual hard drive, which are statistically much more likely to fail) and not so much the RAID card. SAS 6 cards are easy enough to find that it wouldn't be worth the extra cost to buy a "newer" card, especially since there is no reason to expect it to work (or work better) in a T100, not to mention the fact that you probably couldn't "import" the RAID array (virtual disk) into the newer card and would need to do a backup/restore or reinstall.
My T100 is nearly 8 years old and even though it's still running fine, I would like to know which RAID 1 add-on card is a natural upgrade from the SAS 6IR?  Is it the PERC S130?  I don't need anything fancy, just a basic RAID 1 for my small business server.  Thank you.
PowerEdge T100 SAS 6IR upgrade?