Turbo coolant pump (87 MC) source?

[only5kgt@uswest.net]

I commented that I'd lost the turbo coolant after-run pump
due to leaking. It is now bypassed with a brass hose barb-
time to source a new pump, I think. What is the consensus on
the best way to obtain one of these gizmos? (87 5kt, MC)

Beyond the typical "from who, and how much" question:
I understand what the function of this pump is, but how
essential, exactly, is it? At what point was it added- with
the K26 water-cooling changeover?
Does it perform a function in keeping the overall cooling
system temp down- will there be (once the temps rise coming
into spring) problems with the water *not* circulating?
Is the life of the turbocharger in serious jeopardy without
this pump connected? I do "idle down" any time it has been
run at all hard- but I always followed this practice,
regardless of cooling arrangement, on every turbomotor I've
had...

Appreciate any input on this subject.

Regards,
Rob
87 5kt 5-spd 191k (for fun)
68 Schwinn 3-spd (for commuting)