Its not too much work to add the signals, it amounts to breaking down the mirror a bit, and adding the signal and some wiring. Saves a lot of money over buying whole STI mirrors. Junkyards price them high because they came off the STI.
I have extra signals and caps. If you get a set of non-signal mirrors and send them to me I'll convert them to signal mirrors and send them back to you, for a small fee of course. The caps I have are assorted and used so you'd have to have them painted.