One thing a lot of people forget when keeping stacks of 99 is to check the beast vendors as they sell a lot of the items, like I use to keep velveteen cloth till sylph came out, obviously they lack the HQ but does help with a lot of the non normal items that are needed.
I know it isn't a solution and just wish they would let you purchase more retainers or send to your alts directly rather than having to put in an FC chest to transfer (not feasible in a busy FC where chest space is limited) ideal solution let us mail our own alts!