I can see skill tomes and skill upgrade tomes on sale (for non-UMD and UMD).
I was looking to buy a tome to upgrade my +2 inherent bonus to +3 and I cannot find it in the DDO store.
I can see a straight up +3 to UMD.

I can buy a +1 tome then upgrade it all the way to +4 available paying the difference in costs (for non UMD), and for UMD all the way to +2
i.e. buying a +1, then a +1 to +2 then a +2 to +3 and finally a +3 to +4 at the same total cost as buying a +4

Is the 2-3 UMD tome missing or as yet unwritten (not yet available)?
if it's just missing could it please be made available, and obviously at the sale price (20% off).