Thanks, everyone! I found that Granger can get it in a day, so going with
Weld-On 724 and its associated
P70 primer. Pricey, and from what you all say sounds like overkill for pool use, but they're explicitly for caustic substances and work on CPVC as well as PVC, so I figure "do it right and do it once." Plus the heavier-body and slower-setting cement will allow me time to set the four joints I have to do at the same time (lowering the valve + elbow assemblies onto the pipes from the ground,) especially since I can't twist them on.