so kind of a loop/delay - sample/hold thing?
some people really do prefer the old bucket-brigade over digital chips. i for one.
i think it's possible to get classic BBD chips like the MN3005, MN3007, mn3004 etc.
there have been sellers of 'new-old-stock' and i heard that there were operations in china who were pulling used chips from old karoke machines also.
new or used, i also heard that it's important to go for a trusted source.
it's also important to get the clock-chip for driving them.
they're a bit weird in that they operate from a -15 volt supply.
i think you need to include some way to filter out the sound of the clock.
the MN3204 is 512 stage (short) delay, i guess it's a reissue? digikey lists it at least but i don't know if there's a hefty minimum order there.
i'd imagine that the shorter delay chip is what you need.